Patent Publication Number: US-7905045-B1

Title: Mounting assembly with adjustable spring tension

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 11/933,506, Filed Nov. 1, 2007, which is related to and claims priority from earlier filed U.S. Provisional Patent Application No. 60/864,022, filed Nov. 2, 2006. The entire contents of all earlier filed applications are incorporated herein by reference. 
    
    
     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 an accessory mounting assembly, which includes an actuator that is incorporated into the accessory mount in a manner that provides adjustable spring tension to control the clamping force exerted by the actuator against the firearm interface rail. 
     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 is the well-known M16/M4 weapon system (M16 and M4 are trademarks of Colt Defense, Inc.). The M16 has been in service for a number of years and will continue to be a popular rifle both in U.S. and foreign militaries for the foreseeable future. Generally, the M16/M4 weapon  2 , as depicted in  FIG. 1 , includes a lower receiver  4 , upper receiver  6 , butt stock  8 , and barrel  10 . 
     The newer models of the M16/M4 weapons further include a mil-std 1913 dovetail rail  12  extending along the top of the upper receiver. This integrated receiver rail  12  provides a convenient mounting point for many types of enhancement devices such as scopes and other sighting devices. However, space on the upper receiver rail  12  is limited, and many military personnel often have multiple sighting devices that are each tailored to perform in different combat situations. In addition, there are a variety of lighting devices, handgrips, etc. that could also be attached to the weapon for enhanced use of the weapon. The difficulty is that there is simply not enough space on the integrated rail provided on the upper receiver to accommodate all of the desired accessories. Accordingly, 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 include additional mil-std 1913 dovetail rails positioned above or around the barrel of the weapon that can support this important equipment and yet stand the test of rugged military use and abuse. 
     Responding to this need, the applicant has developed a modular integrated rail system (A.R.M.S.® S.I.R.® system) shown at  FIG. 2 , which has been well received by the military and has become popular with several branches of the military. The A.R.M.S. S.I.R. system is fully described in U.S. Pat. No. 6,490,822, the entire contents of which are incorporated herein by reference. These modular integrated rail systems for combat weapons  2  generally include an upper hand guard  14 , a means  16  for securing the upper hand guard  14  to the weapon  2 , a lower firearm accessory  18  (in most cases this is a lower hand guard), various optional rail segments, and in many cases, a sling swivel  20  for attaching a shoulder sling to carry the weapon  2 . 
     The upper hand guard  14  is the main structural element of the system. The upper hand guard is  14  generally semi-cylindrical in shape and has a forward end and a rearward end and a mil-std 1913 dovetail rail  22  extending longitudinally between the forward end and the rearward end. The semi-cylindrical upper hand guard  14  further includes symmetrically opposing side walls that extend outwardly and downwardly from the dovetail rail and terminate in symmetrically opposing longitudinally extending mounting channels. The mounting channels are used to mount various accessories, such as a lower hand guard  18  or a grenade launcher, to the upper hand guard  14 . 
     An interface means  16  is provided at the rearward end of the upper hand guard  14  to removably secure the upper hand guard  14  to the firearm  2 . In the original S.I.R. system as shown in U.S. Pat. No. 6,490,822, the interface includes elongated sleeve that secures the upper hand guard  14  to the dovetail rail  12  on the top of the upper receiver  6  of the weapon  2  as well as a U-shaped yoke or clamp (not shown) that secured the upper hand guard  14  to the barrel nut of the weapon. In the other S.I.R. systems, the interface means  16  is a larger U-shaped yoke or clamp that secures the upper hand guard  14  exclusively to the barrel nut with the upper rail  22  sitting flush with the receiver rail  12 . 
     As is well known in this area, field modification of weapon configurations is critical in combat situations. For example, it may be desired to swap the lower hand guard for a grenade launcher, which can be attached to the upper hand guard, or to add an optional rail segment for securing an added accessory. Similarly, there may be a desire to exchange various different sights or lighting accessories that are mounted on the various dovetail rails positioned around the weapon. In this regard standardized attachment assemblies have been developed to allow quick and easy removal and mounting of these devices relative to the dovetail rails. 
     Such an attachment device is disclosed in U.S. Pat. No. 5,276,988, issued on Jan. 11, 1994 to the present applicant, the contents of the &#39;988 patent being incorporated herein by reference. Generally, the prior art attachment assemblies as shown at  FIGS. 3A and 3B  include a main body  24  having a lower portion that is configured to engage the dovetail rail  22  found on most modern combat weapons  2  and an upper portion  26  that can take on a variety of configurations depending on the accessory that is to be mounted thereon. The lower portion of the mounting assembly has a first engagement member  28  extending downwardly along one side thereof for engaging one side of the dovetail rail  22 . Further, a boss formation  30  is provided adjacent the side of the main body to receive a clamping assembly  32  that is particularly suited to be releasably engaged with a second side of the dovetail rail  22  such that the clamping assembly cooperates with the first engagement member  28  to retain the modular mounting assembly in its installed position on the dovetail rail. The clamping assembly  32  generally includes a foot portion  32 A with a cam surface  32 B to engage the angulated surface of the dovetail rail  22 , a post (not shown) extending upwardly through the boss formation  30  and a head portion  32 C secured to the top end of the post and having actuator arm  32 D to facilitate rotation of the foot portion  32 A. The clamping assembly  32  further includes spring washers (not shown), which are captured between the bottom surface of the head portion  32 C and the boss  30  (or a bushing within the boss) to provide a self-adjusting amount of spring tension as the clamping assembly  32  is rotated into engagement with the rail  22 . These springs generally allow a limited, self-adjusted amount of biased vertical movement of the clamping foot  32 A relative to the boss and the rail  22 . Because the head portion  32 C of the clamping assembly  32  is secured in a fixed position on the top end of the post, the spring are compressed by a fixed amount and therefore the force exerted by the foot  32 A on the rail  22  was generally variable, but variable only within a certain range as determined by the initial spring tension. This small range of self-adjustment is critical in being able to accommodate the small dimensional variations in the dovetail rails of various equipment manufacturers. 
     Further, when such devices are employed with sighting accessories it is critical that the alignment of the device be repeatable and reliable after several removal and reinstallation cycles. If the camming force is too loose, the sight cannot be reinstalled with a high degree of accuracy. Similarly, if the camming force is too great, rotation of the cam foot can damage the rail creating a sloppy fit over time. 
     Finally, despite the benefits of a fixed, self-adjusting range of spring tension provided by the prior art device, in certain environments, there is still a perceived need to adjust the range of the spring tension, for example if rails have excessive wear there may be a need to slightly increase the initial spring tension. However, there is also a desire to prevent the user of the weapon from being able to adjust the tension without some type of restriction. Tighter is not better in these circumstances and over tightening can lead to damage to the rail of the weapon. Accordingly, while a need for adjustment may be accommodated, it should be provided in a manner that accommodates all of the environmental variables while still allowing the accessory mount to be ruggedly attached to the rail. There is thus a struggle between the benefits of a fixed mounting of the head portion  32 C so as to provide a fixed, self-adjusting range of spring tension, and the perceived need to be able to adjust the range of the spring tension. 
     Accordingly, there is a perceived need for a modular mounting assembly that allows for the releasable mounting of various accessories onto the standard dovetail rail found on modern combat weapons and that can be reliably mounted onto a dovetail rail while including an actuator that includes the ability to adjust the spring tension that is exerted by the clamping foot. 
     BRIEF SUMMARY OF THE INVENTION 
     In this regard, the present invention provides for an improved mounting assembly that is configured to be releasably attached to a standard dovetail rail profile wherein the initial clamping tension of the clamping assembly is adjustable. 
     The mounting assembly of the present invention generally includes a main body having a lower portion that is configured to engage the dovetail rail found on most modern combat weapons as depicted in  FIG. 1  and an upper portion that can take a variety of configurations depending on the accessory that is to be mounted thereon. A boss formation including an opening extends outwardly to the side of the main body. A bushing including a central opening is mounted within the opening of the boss formation. The lower portion of the main body has a first engagement member extending downwardly along one side thereof for engaging one side of the dovetail rail. 
     In the scope of the present invention, one embodiment provides an improved clamping assembly that comprises a foot portion positioned adjacent the bottom surface of the boss formation and an actuator arm extending from the foot portion. The foot portion includes a cam surface similar to the prior art foot portion. A shaft affixed to the foot portion extends upwardly through the opening in the bushing. At least one spring (Belleville) washer is received around the shaft adjacent the upper surface of the bushing, and a retention nut is threaded onto the upper end of the shaft such that the spring is captured between the bottom surface of the retention nut and the upper surface of the bushing. The spring washer is compressed as the retention nut is tightened thereby providing for adjustment of the initial spring tension of the clamping assembly. 
     To insure that the retention nut remains in the position set by the user, actuator arm includes a spring-biased indexing pin that engages indexing formations on the outer surface of the retention nut. The indexing formations correspond to different levels of preset tension, i.e. tight, medium and loose. It is this adjustment in the initial spring tension that directly translates to the amount of force with which the clamping assembly engages the rail. Should the user wish to adjust the spring tension, the retention nut is turned until the desired spring tension is achieved. The retention nut also includes mechanical stop that prevents over tightening as well as a shoulder that prevents loosening of the nut once installed. 
     In a second embodiment, the retention nut and indexing pin arrangement is replaced with a through-hole retention nut that itself is self locking, such as a retention nut that includes a nylon locking busing therein. The retention nut is threaded onto the upper end of the shaft such that the spring is captured between the bottom surface of the retention nut and the upper surface of the bushing. The spring washer is compressed as the retention nut is tightened thereby providing for adjustment of the initial spring tension of the clamping assembly. The locking feature of the retention nut itself insures that once the desired spring tension is reached, the nut remains in the same position on the shaft while the actuator arm is operated. 
     In a third embodiment, the spring biased indexing pin is replaced with a threaded locking pin that extends through the actuator arm of the clamping assembly. 
     In a fourth embodiment, a clamping assembly is provided that comprises a foot portion that includes a cam surface similar to the prior art foot portion such that the foot is positioned adjacent the bottom surface of the boss formation. A non-circular shaft is affixed to the foot portion and extends upwardly through the opening in the bushing. At least one spring (Belleville) washer is received around the shaft adjacent the upper surface of the bushing. An actuator arm is engaged with the top portion of the shaft adjacent the top surface of the boss formation such that the at least one spring (Belleville) washer is trapped between the actuator arm and the upper surface of the bushing. A retention nut is threaded onto the upper end of the shaft above the actuator arm such that the actuator arm and the spring is captured between the bottom surface of the retention nut and the upper surface of the bushing. The spring washer is compressed as the retention nut is tightened thereby providing for adjustment of the initial spring tension of the clamping assembly. 
     A fifth embodiment is very similar to the first embodiment with a few additional features including a dual-sided foot and an alternate retention nut with an indexing tool built into the arm of the lever. 
     Accordingly, it is an object of the present invention to provide an improved mounting assembly that allows for the releasable mounting of various accessories onto the standard dovetail rail found on modern combat weapons. Further, it is an object of the present invention to provide a mounting assembly that can be reliably mounted onto a dovetail rail while including an actuator that includes the ability to adjust the spring tension that is exerted by the clamping foot. It is still a further object of the present invention to provide a mounting assembly having an adjustable actuator that further includes a retention nut that allow a user to predictably and reliably control the spring tension and clamping force of the mounting assembly. 
     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 DRAWINGS 
       In the drawings which illustrate the best mode presently contemplated for carrying out the present invention: 
         FIG. 1  is a side view of a prior art combat firearm; 
         FIG. 2  is a perspective view of a prior art rail interface system; 
         FIG. 3A  is an end view of a prior art mounting assembly in the engaged position; 
         FIG. 3B  is an end view of a prior art mounting assembly in the disengaged position; 
         FIG. 4  is an exploded perspective view of a first embodiment of a mounting assembly in accordance with the teachings of the present invention; 
         FIG. 5  is a top view thereof; 
         FIG. 6  is a partial cross-sectional view thereof taken along line  6 - 6  of  FIG. 5 ; 
         FIG. 7  is a perspective view of a second embodiment of a mounting assembly in accordance with the teachings of the present invention; 
         FIG. 8  is an exploded perspective view thereof; 
         FIG. 9  is a partial cross-sectional view there taken along line  9 - 9  of  FIG. 7 ; 
         FIG. 10  is a cross-sectional view of a third embodiment of a mounting assembly in accordance with the teachings of the present invention; 
         FIG. 11  is a perspective view of a fourth embodiment of a mounting assembly in accordance with the teachings of the present invention; 
         FIG. 12  is an exploded perspective view thereof; 
         FIG. 13  is a partial cross-sectional view taken along line  13 - 13  of  FIG. 11 ; 
         FIG. 14  is a perspective view of a fifth embodiment of a mounting assembly in accordance with the teachings of the present invention; 
         FIG. 15  is another perspective view thereof; 
         FIG. 16  is perspective view of the lever and foot of the mounting assembly; 
         FIG. 17  is an exploded perspective view thereof; and 
         FIG. 18  is a cross-sectional view thereof taken along line  18 - 18  of  FIG. 16 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Now referring to the drawings, the mounting assembly is shown and generally illustrated at  40  in  FIGS. 4-6 . The mounting assembly  40  is configured to be releasably attached to a standard dovetail rail profile  12  as is depicted in  FIG. 1 , and includes a means for adjustment to control the clamping force exerted by the mounting assembly  40  against the dovetail rail  12 , as will be discussed in more detail below. The mounting assembly  40  of the present invention is particularly suited for use in connection with any firearm  2  that utilizes a standard dovetail rail  12  or a supplemental rail system. 
     Turning now to  FIG. 4 , as can be seen, the mounting assembly  40  includes a main body  42  that is configured in substantially the same manner as a traditional prior art device and further includes a lower portion  43  that is configured to engage the dovetail rail  12  found on most modern combat weapons  2  and an upper portion  44  that can take on a variety of configurations depending on the accessory that is to be mounted thereon. As can best be seen in  FIG. 6 , the lower portion  43  of the main body  42  has a first engagement member  46  extending downwardly along one side thereof for engaging one side of the dovetail rail  12 . Opposite the first engagement member  46 , a boss formation  48  is provided adjacent the side of the main body  42  wherein the boss formation  48  includes a large central opening  50  therein to receive a clamping assembly generally indicated at  52 . An annular bushing  64  with a smaller central opening  65  is installed into the large central opening  50 . 
     Turning back now to  FIG. 4 , in the scope of the present invention, the clamping assembly  52  replaces the clamping assembly of the prior art as is depicted in  FIGS. 2 and 2   a . In the present invention, the clamping assembly  52  is configured to releasably engage a dovetail rail interface  12  with a self-adjusting clamping force that has an adjustable range of spring tension. The clamping assembly  52  and the first engagement member  46  cooperate to hold the main body  42  on the dovetail rail  12 . 
     The clamping assembly  52  is received into and supported by the boss formation  48  that extends outwardly from the side of the body  42  of the mounting assembly  40 . The clamping assembly  52  generally includes a foot portion  54  that is positioned adjacent the bottom surface of the boss  48  formation. The foot portion  54  includes an angulated cam surface  55  that extends around the side surface of the foot portion  54  as in the prior art devices. However, in contrast to the prior art as described, the actuator arm  56  extends outwardly directly from the foot portion  54  below the boss formation  48  rather then being attached to the foot above the boss formation. The actuator arm  56  allows the user to rotate the foot portion  54  thereby selectively rotating the foot portion  54  between engaged and disengaged positions. A shaft  58  is affixed to and extends upwardly from the foot portion  54  through the smaller opening  65  in the bushing  64  and terminates in a threaded end  60 . 
     At least one spring washer  70  is received around the shaft  58  and is seated on an upper surface of the bottom wall  66  of the bushing  64  within a central recess  68 . The spring washer  70  is preferably a Belleville spring although any other suitable disc-type springs would also fall within the scope of the invention. Further, a plurality of spring washers  70  may be utilized in series, in parallel or in a combination thereof in order to achieve the desired spring tension and deflection properties. 
     A retention nut  62  having a threaded bore  63  is threadedly received on the threaded terminal end  60  of the shaft  58  such the spring washer  70  is captured between the bottom surface of the retention nut and the upper surface of the bottom wall  66  of the bushing  64 . The spring washer(s)  70  is/are compressed as the retention nut  62  is tightened thereby providing for adjustment of the initial spring tension of the clamping assembly  52 . 
     There is also shown a steel buffer pad  72  having a flat horizontal base portion with an arm  74  at each end of the base extending upwardly at an oblique angle of 135 degrees. The free end of each arm  74  is curved approximately 150 degrees. Two side-by-side openings  76 , corresponding in separation to the separation between buffer pad arms  74 , are formed in the main body  42 . The arms  74  of the buffer pad  72  are slid through the openings  76 . In operation, the buffer element  72  sits between the angulated surface of the rail  12  and the cam surface  55  of the foot portion  54 . Rotation of the actuator arm  56  causes the foot portion  54  to press the buffer element  72  into the side of the firearm rail  12 . The buffer element  72  prevents the foot portion  54  from directly touching and thereby marring the outer surface of the firearm rail  12 . Rotation of the actuator arm  56  and the consequent movement of the foot portion  54  against the buffer element  72  overcomes the resistance of the spring washers  70  and moves the buffer element  72  against the engagement surface of the rail interface  12 . 
     To insure that the retention nut  62  remains in a position as set by the user, the clamping assembly  52  further comprises an indexing means for positively indexing the position of the retention nut  62  on the threaded shaft  58 . The indexing means preferably comprises at least one indexing formation (detent)  82  on the outer edge surface  80  of the retention nut  62  and a spring-biased indexing pin  84 . The indexing pin  84  is received within a bore  85  formed in the handle portion of the actuator arm  56 . A small spring  87  is captured between the inner end of the indexing pin  84  and the inner end of the bore  85  to bias the pin  84  outwardly towards the retention nut  62 . 
     Preferably the retention nut  62  includes a plurality of indexing formations  82 . Even more preferably, the retention nut  62  includes three indexing formations  82  corresponding to three levels of preset tension, i.e. tight, medium and loose. 
     Since the spring washer(s)  70  are trapped between the retention nut  62  and the bushing  64 , tightening of the retention nut  62  causes compression of the spring washers  70 , shortens the range of the vertical travel of the foot portion  54  relative to the bottom surface of the boss and increases the spring clamping force. Accordingly, when the actuator arm  56  rotates the foot portion  54  into engagement with the rail  12 , additional spring pressure is exerted on dovetail rail  12 . Similarly, as the retention nut  62  is loosened, the compression of the disc springs  70  is reduced, the range of vertical travel of the foot portion  54  is increased, and the clamping force is reduced. 
     It is this adjustment in the initial spring tension that directly translates to the amount of force with which the clamping assembly  52  engages the rail  12 . Should the user wish to adjust the spring tension, the spring-loaded pin  84  is either depressed, or withdrawn in a manner that allows rotation of the retention nut  62 , and the retention nut  62  is then turned until the desired spring tension is achieved. The pin  84  is then released and it again engages one of the indexing formations  82  in the surface of the retention nut  62  preventing inadvertent rotation thereof. 
     In order to prevent removal of the retention nut  62  once installed, the edge of the retention nut  62  include a stop shoulder  86  with a ramped surface  86 A on one side and a flat edge  86 B on the other. The ramped surface  86 A is arranged so that as the retention nut  62  is tightened the pin  84  rides up and over the ramp surface  86 A. However, the flat edge  86 B of the shoulder  86  prevents inadvertent or accidental loosening (counterclockwise rotation) of the retention nut  62 . 
     Further, to prevent over-tightening of the retention nut  62 , the threaded bore  63  contains a positive mechanical stop. Preferably, the threaded bore  63  does not extend all the way through the retention nut  62  and includes and end wall  88  or a reduced diameter area that prevents over tightening of the retention nut  62 . In this regard, the retention nut  62  can be installed until it bottoms out on the shaft  58  and thereafter can be backed off to one of the three predetermined settings corresponding to the indexing formations  82 . 
     Turning now to  FIGS. 7 ,  8  and  9 , a second embodiment of the mounting assembly  140  can be seen to include a main body  142  that is configured in substantially the same manner as a traditional prior art device and further includes a lower portion  143  that is configured to engage the dovetail rail  12  found on most modern combat weapons  2  and an upper portion  144  that can take on a variety of configurations depending on the accessory that is to be mounted thereon. As can best be seen in  FIG. 9 , the lower portion  143  of the main body  142  has a first engagement member  146  extending downwardly along one side thereof for engaging one side of the dovetail rail  12 . Opposite the first engagement member  146 , a boss formation  148  is provided adjacent the side of the main body  142  wherein the boss formation  148  includes a large central opening  150  therein to receive a clamping assembly generally indicated at  152 . An annular bushing  164  with a smaller central opening  165  is installed into the large central opening  150 . 
     As provided above, the clamping assembly  152  is received into and supported by the boss formation  148 . The clamping assembly  152  generally includes a foot portion  154  that is positioned adjacent the bottom surface of the boss  148  formation. An actuator arm  156  extends outwardly directly from the foot portion  154  below the boss formation  148  wherein the actuator arm  156  allows the user to rotate the foot portion  154  thereby selectively rotating the foot portion  154  between engaged (parallel to main body  142 ) and disengaged (perpendicular to main body  142 ) positions. The boss formation  148  includes a shoulder  149  configured to prevent rotation of the actuator arm  156  beyond the disengaged position (perpendicular to main body  142 ). 
     A shaft  158  is affixed to and extends upwardly from the foot portion  154  through the smaller opening  165  in the bushing  164  and terminates in a threaded end  160 . Further, at least one spring washer  170  can be seen received around the shaft  158  and seated within the bushing  164 . A retention nut  162  having a threaded bore  163  is threadedly received on the threaded terminal end  160  of the shaft  158  such the spring washer(s)  170  is/are captured between the bottom surface of the retention nut  162  and the upper surface of the bottom wall of the bushing  164 . The spring washer(s)  170  is/are compressed as the retention nut  162  is tightened thereby providing for adjustment of the initial spring tension of the clamping assembly  152 . The retention nut  162  further includes a self-locking nylon bushing  166  on the bottom end thereof to firmly lock the retention nut  162  in place once tightened to the desired resistance. The outside surface of the retention nut  162  includes a knurled or textured surface  167  to facilitate hand-tightening of the nut  162 . Further, the top end of the nut  162  includes a transverse slot  168 , preferably having the size of a quarter, which will permit tightening of the retention nut  162  with any available flat sided implement, such as for example, a coin, a screwdriver, a bayonet, etc. 
     There is also shown a steel buffer pad  172  having a flat horizontal base portion with an arm  174  extending upwardly at an oblique angle of 135 degrees relative to the base. The free end of each arm  174  is curved approximately 150 degrees. Two side-by-side openings  176 , corresponding in separation to the separation between buffer pad arms  174 , are formed in the main body  142 . The arms  174  of the buffer pad  172  are slid through the openings  176 . In all respects, the buffer pad  172  operates as described in the first embodiment above. 
     Turning to  FIG. 10 , a third embodiment of the mounting assembly can be seen, and is generally indicated at  140 A. The third embodiment is similar to the previous embodiment  140 , including the same general components, main body  142 , clamping assembly  152 , etc. The differences are found in the manner of locking the retention nut  162  relative to the cam foot  154 . Retention nut  162  no longer includes the nylon bushing  166 . Rather, the nylon bushing  166  is replaced with a threaded locking pin  180  including a shaft  182  which passes through a bore  184  in a modified actuator arm  156 . It can be seen that the actuator arm  156  is taller in dimension, rising up to the same level as the top of the retention nut  162 . The shaft  182  has a head portion  186  that extends from the front end of the arm  156  and engages with the knurled (grooved) side surface of the retention nut. More specifically, the head portion  186  can sit within the individual grooves  190  (see  FIG. 8 ) to prevent rotation of the retention nut  162 . The tail end of the shaft  182  includes a threaded portion  192 , threadedly received into a threaded bore  194  in the terminal end of the arm  156 . The locking pin  180  can thus be rotated to extend and retract the head  186  of the pin  180  to lock and unlock the retention nut  162 . 
     Turning to  FIGS. 11 ,  12  and  13 , a fourth embodiment of the mounting assembly  240  can be seen to include a main body  242  that is configured in substantially the same manner as a traditional prior art device and again includes a lower portion  243  that is configured to engage the dovetail rail  12  found on most modern combat weapons  2  and an upper portion  244  that can take on a variety of configurations depending on the accessory that is to be mounted thereon. As can best be seen in  FIG. 13 , the lower portion  243  of the main body  242  has a first engagement member  246  extending downwardly along one side thereof for engaging one side of the dovetail rail  12 . Opposite the first engagement member  246 , a boss formation  248  is provided adjacent the side of the main body  242  wherein the boss formation  248  includes a large central opening  250  therein to receive a clamping assembly generally indicated at  252 . An annular bushing  264  with a smaller central opening  265  is installed into the large central opening  250 . 
     As provided above, the clamping assembly  252  is received into and supported by the boss formation  248 . However, in this embodiment, the clamping assembly  252  generally includes a foot portion  254  that is positioned adjacent the bottom surface of the boss  248  formation. A shaft  258  is affixed to and extends upwardly from the foot portion  254  through the smaller opening  265  in the bushing  264  and terminates in a threaded end  260 . The lower portion of shaft  258  is formed in a hexagonal shape to key the actuator arm  256 . At least one spring washer  270  can be seen received around the shaft  258  and seated within the bushing  264 . In contrast to the previous embodiments, the actuator arm  256  engages the shaft  258  above the boss formation  248  wherein a hexagonal keyed opening  257  in the actuator arm  256  engages the shaft  258  and allows the user to turn the foot portion  254  thereby selectively rotating the foot portion  254  between engaged and disengaged positions. The boss formation  248  includes a shoulder  249  configured to prevent rotation of the actuator arm  256  beyond the disengaged position (perpendicular to main body  242 ). 
     A retention nut  262  having a threaded bore  263  is threadedly received on the threaded terminal end  260  of the shaft  258  such the actuator arm  256  is captured below the bottom surface of the retention nut  262  and in turn captures the spring washer  270  between the actuator arm  256  and the upper surface of the bottom wall of the bushing  264 . The spring washer(s)  270  is/are compressed as the retention nut  262  is tightened thereby providing for adjustment of the initial spring tension of the clamping assembly  252 . The retention nut  262  further includes a self-locking nylon bushing  266  on the bottom end thereof to firmly lock the retention nut  262  in place once tightened to the desired resistance. The outside surface of the retention nut  262  includes a knurled or textured surface  267  to facilitate hand-tightening of the nut  262 . Further, the top end of the nut  262  includes a transverse slot  268 , preferably having the size of a quarter, which will permit tightening of the retention nut  262  with any available flat sided implement, such as for example, a coin, a screwdriver, a bayonet, etc. Finally, as provided above, a steel buffer pad  272  is provided that also operates as described in the first embodiment above. 
     Turning to  FIGS. 14-18 , a fifth embodiment of the invention is illustrated and generally indicated at  340 . The fifth embodiment is most similar to the first embodiment  40  with a few additional features. 
     The mounting assembly  340  includes a main body  342  that is configured in substantially the same manner as a traditional prior art device and further includes a lower portion  343  that is configured to engage the dovetail rail  12  found on most modern combat weapons  2  and an upper portion  344  that can take on a variety of configurations depending on the accessory that is to be mounted thereon. In the embodiment shown, the upper surface  344  is configured to receive an ACOG scope (ACOG is a registered trademark of Trijicon, Inc.). The lower portion  343  of the main body  342  has a first engagement member  346  extending downwardly along one side thereof for engaging one side of the dovetail rail  12 . Opposite the first engagement member  346 , a boss formation  348  is provided adjacent the side of the main body  342 . An annular bushing  364  is installed into the opening of the boss  348 . 
     The clamping assembly  352  generally includes a foot portion  354  that is positioned adjacent the bottom surface of the boss  348  formation. The foot portion  354  includes an angulated cam surface  355  that extends around the side surface of the foot portion  354  as in the prior art devices. In contrast to the first embodiment  40 , the foot portion  354  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. The actuator arm  356  extends outwardly directly from the foot portion  354  below the boss formation  348  and allows the user to rotate the foot portion  354  between engaged ( FIG. 14 ) and disengaged ( FIG. 15 ) positions. A shaft  358  is affixed to and extends upwardly from the foot portion  354  through the bushing  364  and terminates in a threaded end  360 . 
     At least one spring washer  370  is received around the shaft  358  and is seated on the bottom wall of the bushing  364 . 
     A retention nut  362  having a threaded bore  363  is threadedly received on the threaded terminal end  360  of the shaft  358  such the spring washer  370  is captured between the bottom surface of the retention nut and the upper surface of the bottom wall of the bushing  364 . The spring washer(s)  370  is/are compressed as the retention nut  362  is tightened thereby providing for adjustment of the initial spring tension of the clamping assembly  352 . 
     There is also shown a steel buffer pad  372  as found in the earlier embodiments. 
     To insure that the retention nut  362  remains in a position as set by the user, the clamping assembly  352  further comprises an indexing means for positively indexing the position of the retention nut  362  on the threaded shaft  358 . The indexing means preferably comprises at least one indexing formation (detent)  382  on the outer edge surface  380  of the retention nut  362  and a spring-biased indexing pin  384 . As shown in the embodiment, the detentss  382  extend all the way around the outer surface  380  of the retention nut to provide a wide range of adjustment. The indexing pin  384  is received within a bore  385  formed in the handle portion of the actuator arm  356 . A small spring  387  is captured between the inner end of the indexing pin  384  and a roll pin  388  extending across the bore  385  to bias the pin  384  outwardly towards the retention nut  362 . The indexing pin  384  is further held within the bore  385  by another roll pin  390  extending across the bore and across a slot formed on the indexing pin  385 . The slot provides a short amount of travel of the pin  384  but prevents it from falling out. 
     Since the spring washer(s)  370  are trapped between the retention nut  362  and the bushing  364 , tightening of the retention nut  362  causes compression of the spring washers  370 , shortens the range of the vertical travel of the foot portion  354  relative to the bottom surface of the boss and increases the spring clamping force. Accordingly, when the actuator arm  356  rotates the foot portion  354  into engagement with the rail  12 , additional spring pressure is exerted on dovetail rail  12 . Similarly, as the retention nut  362  is loosened, the compression of the disc springs  370  is reduced, the range of vertical travel of the foot portion  354  is increased, and the clamping force is reduced. 
     Rotation of the retention nut  362  is facilitated by a plurality of radial bores  392  formed in the nut  362  and a lever tool  394  which is hidden within the handle of the arm  356 . The tool  394  is frictionally retained within the bore and is removed for rotation of the nut  362  only when required. The terminal end of the tool is fitted into one of the radial holes  392  and provides leverage for rotation of the nut  362 . 
     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.