Mounting assembly with adjustable spring tension

[0001] 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.

[0002] 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.

[0003] 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.

[0004] 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.

[0005] 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.

[0006] 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.

[0007] 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.

[0008] 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.

[0009] 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 '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 32A with a cam surface 32B 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 32C secured to the top end of the post and having actuator arm 32D to facilitate rotation of the foot portion 32A. The clamping assembly 32 further includes spring washers (not shown), which are captured between the bottom surface of the head portion 32C 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 32A relative to the boss and the rail 22. Because the head portion 32C 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 32A 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.

[0010] 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.

[0011] 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 32C 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0043] 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.

[0044] 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.

[0045] 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 2a. 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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 86A on one side and a flat edge 86B on the other. The ramped surface 86A is arranged so that as the retention nut 62 is tightened the pin 84 rides up and over the ramp surface 86A. However, the flat edge 86B of the shoulder 86 prevents inadvertent or accidental loosening (counterclockwise rotation) of the retention nut 62.

[0055] 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.

[0056] 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.

[0057] 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).

[0058] 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.

[0059] 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.

[0060] Turning to FIG. 10, a third embodiment of the mounting assembly can be seen, and is generally indicated at 140A. 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.

[0061] 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.

[0062] 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).

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] At least one spring washer 370 is received around the shaft 358 and is seated on the bottom wall of the bushing 364.

[0068] 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.

[0069] There is also shown a steel buffer pad 372 as found in the earlier embodiments.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.