Abstract:
A mounting assembly for attaching an accessory to a dovetail rail interface on a firearm includes a body having a lower portion and an upper portion. The lower portion is configured to engage the dovetail rail interface and the upper portion is configured to receive and retain an accessory such as a scope or aiming device. A spring dampening structure resides within the body of the assembly wherein dampening structure is configured to dampen shock waves and harmonic vibration transferred into the body from operation of the firearm. A clamping assembly is configured to releasably clamp the body to the dovetail rail interface.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to modular integrated accessory mounting assemblies for combat weapons. More specifically, the present invention relates to a unique dampening structure incorporated into an accessory mount in a manner that dampens shock waves and the resulting harmonic vibration cause by operation of the firearm. 
     As the field of combat and commercial weaponry expands, numerous add-on enhancements have become available for attachment to standard firearms, thereby significantly upgrading the capability of the firearm. Of particular interest in the area of combat weapons are the well-known M16/M4 weapon systems (M16 and M4 are trademarks of Colt Defense, Inc.), the FNH™ SCAR™ weapon system (FN and SCAR are trademarks of FN Herstal, S.A., and the Barrett™ family of high caliber sniper weapons (Barrett is a trademark of Barrett Firearms Mfg., Inc.). However, the concepts of the present invention are equally applicable to all firearms, weapon systems, and add-on enhancements. In particular, the concepts of the present invention are most applicable to larger caliber service weapons such as the 50 caliber Barrett™ M82A1 rifle. For purposes of illustration only, we refer to  FIG. 1 , which shows an image of the M82A1 rifle generally indicated at  10 . The weapon  10  generally includes a receiver  12 , stock  14 , and barrel  16 . 
     Most modern combat weapons further include a mil-std  1913  dovetail rail  18  extending along the top of the receiver. This integrated receiver rail provides a convenient mounting point for many types of enhancement devices such as scopes  20  and/or other sighting devices. The increasing development and refinement of laser sights, infrared lighting, visible lighting, night vision, and specialized scopes and magnifiers, and other accessories continues to drive the need for versatile and reliable integration systems that can support this important equipment and yet stand the test of rugged military use and abuse. 
     One of the issues of mounting sensitive electro-optic components on a weapon is that shock waves and harmonic vibration resulting from operation of the weapon are transmitted through the weapon and mounts into the mounted component. Shock waves and the resultant harmonic vibrations that travel through the mechanical structures of the weapon will fatigue, damage or destroy almost any electro-optical device over time. While some of the sighting devices that are employed with a firearm may be able to endure the shocks, many more are damaged and ultimately fail as a result of the transferred shock waves and harmonic vibration. All branches of the military are reporting increased instances of field failure of these expensive, highly sensitive optic components on all types of weapons. However, failures are particularly distinguished on the more powerful, higher caliber weapons. 
     Before proceeding, we need to distinguish “recoil” from “shock waves” and “vibration”. Simply put, “recoil” is the backward push of a firearm. According to Newton&#39;s third law of motion, for every action there is an equal and opposite reaction. Recoil is thus an equal but opposite reaction of the weapon to the forward momentum of the projectile exiting the barrel. The expanding gas of the burning powder causes recoil. It forces the bullet out of the case and down the barrel and exerts an equal force back against the rear of the chamber. The force is the same in both directions. 
     Modern autoloading (automatic or semi-automatic) weapons have the same measured recoil as bolt action weapons, but the “kick” felt by the shooter is less for some types of actions. The spring systems that are used to cycle the weapon and load the next cartridge operate to distribute some of the recoil thrust that would be felt by the shooter. 
     In addition to recoil, every weapon also experiences higher frequency shock waves and harmonic vibration caused by slamming of the moving parts of weapon against each other. Webster&#39;s dictionary defines a “wave” as a disturbance that transfers energy progressively from point to point in a medium and may take the form of an elastic deformation of the medium. For purposes of this invention, the most important part of this definition is that a wave is a “disturbance” which travels through a medium. The medium through which the wave travels may experience local oscillation as the wave passes. Vibration refers to mechanical oscillations about an equilibrium point. Vibration is occasionally desirable, such as the motion of a tuning fork. More often, vibration is undesirable, wasting energy and creating unwanted disturbances. Free vibration occurs when a mechanical system is set off with an initial input (wave) and then allowed to vibrate freely. The mechanical system will then vibrate at its natural frequency and gradually damp down to zero. The simplest analogy is the ringing vibration of a piece of metal when struck by a hammer. 
     Referring now to  FIG. 2 , a set of 3 graphs depicts the magnitude of shock waves experienced by an M82A1 (50 caliber) sniper rifle firing a single round. Each graph represents a measurement along a linear axis with the x-axis extending lengthwise along the weapon, the y-axis extending transversely across the weapon, and the z-axis extending vertically through the weapon. Each graph is set out with acceleration on the y-axis and time on the x-axis. There are three distinct events that generate shock waves in this semi-automatic weapon. First, the discharge of the cartridge creates an initial shock wave (event  1 )  22 . Second, the gas blow-back slams the bolt backward against the buffer spring, bottoming out against the bottom of the spring cavity (event  2 )  24 . Finally, the buffer spring sends the bolt forwardly slamming it into the rear end of the barrel to seat another round in the chamber (event  3 )  26 . 
     While existing buffer spring systems are intended to capture the energy of the rearward thrust of the bolt, they are not designed to dampen higher frequency shock waves and harmonic vibrations, which are distinctly different from recoil. 
     The prior art uncovered by the Applicant seeks to address the effects of recoil on scope mounts. Typically, these systems introduce a spring element that sits between the mount body and the rings and allows cushioned movement of the rings (and scope) longitudinally relative to the mount body. 
     U.S. Pat. No. 2,510,289 to Livermore discloses such a mounting system wherein a spring tube is positioned between the bases of the rings and the mount body to provide a cushioned buffer against recoil. 
     U.S. Pat. No. 2,710,453 to Beverly discloses another such mounting system where a compression spring is seated between a fixed pin and a movable pin to both allow the scope to be swung to one side and to be removed from the base. 
     U.S. Pat. No. 6,678,988 to Poff discloses yet another such mount where a lower rail portion is fixedly mounted on the weapon and an upper rail portion slidably moved relative to the lower rail portion. A scope is mounted on the upper rail. A pair of compression springs cushion forward and rearward movement of the upper rail relative to the lower rail caused by recoil. French Patent FR2588370 is very similar to Poff in many respects. 
     U.S. Pat. No. 7,013,593 to Pettersson is directed to a holder device including springs that reduce axial recoil motion. 
     The Applicant&#39;s own U.S. Pat. No. 4,845,871 is cited for its disclosure of a pair of Belleville springs that are situated between a cam foot and a base to hold the mount in place. These springs are not intended to absorb recoil shock. However, they do provide a softer, cushioned interface between the hard mount and attachment rail of the weapon. 
     While each of the devices of the prior art is generally effective for its intended purpose, i.e. absorbing recoil thrust, none are directed at the unique problem of absorbing high frequency shock waves and harmonic vibration, which can destroy sensitive electro-optic devices. 
     SUMMARY OF THE INVENTION 
     The present invention seeks to provide a unique dampening structure incorporated into an accessory mount in a manner that dampens shock waves and the resulting harmonic vibration cause by operation of the firearm. 
     The dampening structure can be used as a stand alone device for independently absorbing and dissipating shock waves and harmonic vibration generated by the weapon, i.e. separate and apart from a mount for an accessory, but is more preferably integrated into the body of a mount used to attach a particular accessory to a weapon. In this manner the dampening structure can be tuned and adapted for the best performance with respect to the mounted accessory. 
     A mounting assembly for attaching an accessory to a dovetail rail interface comprises a body having a lower portion and an upper portion. The lower portion is configured and arranged to engage a first side of the dovetail rail while the upper portion configured to receive and retain an accessory, such as a scope mount. In this regard, in one of the preferred embodiments, the upper portion includes a pair of rings that clamp around the tube of a telescopic sight. A dampening structure is incorporated within the body of the mount where it is configured to dampen shock waves and harmonic vibration transferred into the body from operation of the firearm. More specifically, the dampening structure comprises a spring, which is captured within a bore or channel extending longitudinally within the body. More specifically, the spring is a coil spring, although other types of springs are contemplated. The spring is at least partially compressed and the compression can be adjusted by means of a threaded captivating nut received in the open end of the bore. 
     Extending outwardly from the side surface of the body is a boss formation including an opening therein which serves as a platform for a clamping assembly. The clamping assembly extends through the opening in the boss and is configured to releasably engage a second side of the dovetail rail. More specifically, the clamping assembly includes a foot portion positioned adjacent a bottom surface of the boss formation. The foot portion includes a cam surface. 
     To provide movement of the foot, an actuator arm extends outwardly from the foot portion. A shaft extends upwardly from the foot portion through the opening in the boss formation where a spring is received around the shaft adjacent the top surface of the boss formation. A retention nut is threadedly received on a terminal end of the shaft such that the spring is captured between a bottom surface of the retention nut and a top surface of the boss formation. 
     To insure that the retention nut stays in the position set by the user, a locking pin is threadedly received through a bore in the actuator arm. The locking pin is configured and arranged to allow a user to positively lock the position of the retention nut on the threaded shaft. 
     In operation, movement of the clamping assembly to releasably engage the dovetail rail causes the foot portion to clamp against the second side of the dovetail rail. 
     Accordingly, it is a core object of the invention to provide a dampening structure that can be mounted onto a weapon for the purpose of absorbing shock waves and harmonic vibration generated by operation of the weapon. 
     It is a further object of the invention to provide a mounting assembly for mounting accessories to a weapon wherein the mount includes an integrated dampening structure for absorbing shock waves and harmonic vibration generated by operation of the weapon. 
     It is yet another object of the invention to provide such a mounting assembly where the dampening structure is a coil spring extending longitudinally, parallel to the long axis of the weapon. 
     These, together with other objects of the invention, along with various features of novelty that characterize the invention, are pointed out with particularity in the claims annexed hereto and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated a preferred embodiment of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       The invention will now be described further by way of example with reference to the following examples and figures, which are intended to be illustrative only and in no way limiting upon the scope of the invention. 
         FIG. 1  shows a plan view of an M82A1 sniper rifle; 
         FIG. 2  shows a set of graphs depicting  3  separate shock wave events generated by the firing of a single round; 
         FIG. 3  shows a perspective view of a mount constructed in accordance with the teachings of the present invention; 
         FIG. 4  is another view thereof showing the clamping assembly partially exploded; 
         FIG. 5  is a right side view thereof; 
         FIG. 6  is a cross-sectional view thereof taken along line  6 - 6  of  FIG. 3 ; 
         FIG. 7  is another perspective view thereof showing the dampening structure exploded; 
         FIG. 8  is a perspective view of a dampening mount constructed in accordance with the teachings of the present invention; and 
         FIG. 9  is a graph showing experimental test data. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Now referring to the drawings, a mounting assembly constructed in accordance with the teachings of the present invention is shown and generally illustrated at  100  in  FIGS. 3-7 . 
     The mounting assembly  100  generally includes a body  102 , a dampening structure  104 , and a clamping assembly  106 . It is noted that the illustrated mount includes a pair of clamping assemblies  106 . However, for purposes of this description we will refer to a single clamping assembly  106 . 
     The body  102  includes a lower portion  108  that is configured to engage the dovetail rail  18  found on most modern combat weapons and an upper portion  110  that can take on a variety of configurations depending on the accessory that is to be mounted thereon. The lower portion  108  of the body has a pair of first engagement members  112  extending downwardly along one side thereof for engaging one side of the dovetail rail  18 . Opposite the first engagement members  112 , a boss formation  114  is provided adjacent the side of the body  102 . An annular bushing  116  is installed into the opening of the boss  114 . 
     Referring to  FIGS. 3-6 , the upper portion of the body is provided at each end with rings  118  for receiving and holding a telescopic sight (not shown). The rings  118  are held in place by screws  120  received through the body  102  but are otherwise conventional within the art and no further explanation is believed to be needed. 
     In accordance with the teachings of the present invention and as can best be seen in the side and cross sectional views ( FIGS. 5 and 6 ), the upper portion  110  of the body  102  includes a longitudinal channel  122  or borehole formed therein. Preferably, the borehole  122  extends longitudinally within the body  102  parallel to the longitudinal extent of the firearm on which it will be mounted. A dampening structure  14 , preferably a coil spring, is received within the borehole  122  and is seated against the bottom wall thereof. A captivating plug  124  is then received into the open end of the channel/borehole to retain the spring  14  therein. Preferably, the captivating plug  124  is threadably received within the open end of the channel or bore  122 . The captivating plug  124  further preferably at least partially compresses the spring  14  within the channel or bore  122 . A second plug  126  is received is received in the open end of the bore to close off the end of the bore  122 . 
     The spring  104  positioned within the main body  102  acts as a dampener to absorb shock waves and harmonic vibration generated by the firearm and reduces the transfer of those shocks to the accessory retained on the mount  100 . 
     While a coil spring  104  is illustrated herein as the preferred embodiment, the disclosure should not be considered to be limiting to this embodiment. Depending on the type of weapon and the measured shock wave and harmonic vibration as generated by the particular weapon, different types and variations of spring dampeners  104  may be utilized, including but not limited to accordion springs, bellevile-type springs, and leaf springs, as well as resilient or elastic materials such as silicone, cork, and polymeric foams. Likewise, while the orientation of the spring is indicated at being longitudinal in the preferred embodiment, the orientation should not be limited to this configuration. The dampening structure  104  may be oriented in whatever direction the largest shock wave is measured. This could potentially be horizontal or vertical or at an angle to the mount. In addition, the disclosure should not be considered to be limited to the use of a single dampening structure, nor should it be limited to the use of a single dampening structure extending in a single direction. Compound dampening may require the use of several different dampening structures extending in different directions as the situation may require. Experimentation and testing is required to determine the direction and magnitude of the shock waves and harmonic vibration of a particular weapon. 
     The clamping assembly  106  generally includes a foot portion  128  that is positioned adjacent the bottom surface of the boss formation  114 , a spring  130 , a retention nut  132  and a buffer pad  134 . The foot portion  128  includes an angulated cam surface  136  that extends around the side surfaces of the foot portion  128  as in the prior art devices. The foot portion  128  is configured as a dual sided foot so that only one foot and arm need be provided for both left and right hand mounting assemblies. An actuator arm  138  extends outwardly directly from the foot portion below the boss formation  114  and allows the user to rotate the foot portion  128  between engaged and disengaged positions. A shaft  140  is affixed to and extends upwardly from the foot portion  128  through the bushing  116  and terminates in a threaded end  142 . 
     Spring  130  in the form of a coil spring or spring washer is received around the shaft  140  and is seated on the bottom wall of the bushing  116 . 
     The retention nut  132  having a threaded bore is threadedly received on the threaded terminal end  142  of the shaft  140  such that the spring  130  is captured between the bottom surface of the retention nut  132  and the upper surface of the bottom wall of the bushing  116 . The spring  130  is compressed as the retention nut  132  is tightened thereby providing for adjustment of the initial spring tension of the clamping assembly  106 . 
     It is noted that this spring arrangement  130  contained within the clamping assembly  106  provides at least some additional dampening in the vertical axis, although the size and significant compression of the spring limits the amount of dampening this spring can provide. 
     In order to protect the soft aluminum rails  18  of the weapon  10 , the steel buffer pad  134  is pivotably received adjacent the cam surface  136  of the foot  128 . 
     To insure that the retention nut  132  remains in a position as set by the user, the clamping assembly  106  further comprises a locking mechanism  144  for positively locking the position of the retention nut  132  on the threaded shaft  140 . The locking mechanism  144  preferably comprises at least one locking formation (detent)  146  on the outer edge surface of the retention nut  132  and a threaded locking pin  148 . As shown in this embodiment, the detents  146  extend all the way around the outer surface of the retention nut  132  to provide a wide range of adjustment. The locking pin  148  is received within a bore formed in the handle portion of the actuator arm  138 . Threads on the proximal end of the locking pin  148  adjacent a head portion of the locking pin engage complimentary threads within the bore in the actuator arm  138 . While the locking pin  148  can be displaced inwardly and outwardly relative to the actuator arm  138 , the locking pin  148  is further held within the bore by a roll pin  150  extending across the bore and across a shoulder region slot formed on the locking pin. The shoulder region provides a sufficient amount of travel for retraction and engagement of the pin but prevents it from falling out. 
     Since the spring  130  is trapped between the retention nut  132  and the bushing  116 , tightening of the retention nut  132  causes compression of the spring  130 , shortens the range of the vertical travel of the foot portion  128  relative to the bottom surface of the boss  114  and increases the spring clamping force. Accordingly, when the actuator arm  138  rotates the foot portion  128  into engagement with buffer pad  134  and in turn the rail  18 , additional spring pressure is exerted on dovetail rail. Similarly, as the retention nut  132  is loosened, the compression of the spring  130  is reduced, the range of vertical travel of the foot portion  128  is increased, and the clamping force is reduced. In order to tighten or loosen the retention nut  132 , the locking pin  148  is unthreaded relative to the actuator arm  138  until the distal end of the locking pin  148  is clear of the detents  146  in the retention nut  132  thereby allowing rotation of the retention nut  132  relative to the clamping assembly  106 . After the retention nut  132  is adjusted and the desired spring tension is set, the locking pin  148  is threaded back into the bore such that the distal end of the locking pin engages one of the detents  146  on the retention nut  132  preventing rotation of the retention nut  132  relative to the clamping assembly  106 . 
     It can further be appreciated that the head at the proximal end of the locking pin  148  includes a texturing or knurling thereon as well as an increased diameter to facilitate turning of the locking pin by hand. 
     Referring now to  FIG. 8 , a single graph shows the side-by-side results obtained from accelerometer sensors mounted on three different configurations of an M107 sniper rifle. The results illustrated show shock wave and harmonic vibration measured along the x-axis (the longitudinal extent of the weapon parallel to the barrel). The results to the far left (M107 Rail Mounted) are measurements taken directly from sensor mounted directly on the rail interface of the weapon. The results in the middle (Solid Steel Rings) are measurements taken from sensors mounted on a set of steel rings mounted on the rail interface of the weapon. The left and middle results show that much of the shock and vibration experienced by the weapon is directly transferred into the rings, and thus into the telescopic sight clamped in the rings. The results to the far right (A.R.M.S. #72 Mount w/Dampening Spring) are measurements taken from sensors mounted on the preferred embodiment of the invention as illustrated herein ( FIGS. 3-7 ). 
     The goal of the testing was to capture and characterize the shock/harmonic events and evaluate the benefits of the dampening structure within the mount of the invention versus an old fashioned hard mounting rings. The right hand graph clearly demonstrates that the present invention offers a drastic reduction (&gt;2×) in initial shock impact to an electro optical device, as well as a reduced overall harmonic vibration energy when compared to traditional sold hard mount rings. 
     Turning to  FIG. 9  there is shown an alternative embodiment  200  which can be used as a stand-alone dampening device independent of any particular accessory. The dampening device  200  can be mounted on any weapon as an ancillary device for the purpose of absorbing shock waves and harmonic vibration and protecting another accessory mounted onto the weapon using a different mounting system. For example, if a scope is mounted onto a weapon using conventional rings, the present dampening device  200  could be used in conjunction with the ring mounting system to provide dampening of the shock waves and harmonic vibration within the weapon to reduce the level of shock and vibration to be transferred into the existing ring mounts. In this regard, the dampening device  200  is which is virtually identical to the first embodiment  100 , except that the rings have been removed. Such a dampening device  200  could be mounted on a rail interface adjacent to the sighting device or at another location. Certain locations may be found to have better performance than others as determined by experimental data and testing. 
     Accordingly, it can be seen that the present invention provides a unique and novel modular accessory mount that fills a critical need for soldiers in the field by ensuring positive and reliable operation. For these reasons, the instant invention is believed to represent a significant advancement in the art, which has substantial commercial merit. 
     While there is shown and described herein certain specific structure embodying the invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described except insofar as indicated by the scope of the appended claims.