Patent Publication Number: US-7222451-B2

Title: Quick disconnect bipod mount and clamp assembly

Description:
RELATED PATENT AND PENDING PATENT APPLICATION INFORMATION 
   This application claims priority to provisional patent application No. 60/543,572, filed Feb. 12, 2004, the entire disclosure of which is incorporated herein by reference. This application is owned by the applicant/owner of U.S. Pat. No. 5,711,103 and U.S. Pat. No. 5,815,974, the entire disclosures of which are incorporated herein by reference. Additionally, this application is owned by the applicant/owner of provisional application No. 60/338,153, filed Nov. 13, 2001, the entire disclosure of which is also incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an apparatus and method useful as firearm accessories and support devices such as bipods, and more particularly, relates to a clamp assembly for attaching an accessory to a mounting rail structure affixed to the forearm stock of a firearm. The clamp assembly attaches to the rail structure and enables quick attachment and detachment of the accessory to the firearm without modification of the rail structure or forearm stock of the firearm. 
   2. Background of the Invention 
   When shooting firearms, especially in stressful tactical situations, it is important that the firearm be maintained in a steady, stable position to insure accuracy of aim. Most shooters are not able to hold a firearm consistently in a set position without wavering, especially after the onset of fatigue resulting from strain on the shooter due to the size and weight of the firearm. 
   Accordingly, peripheral support devices have been used in conjunction with firearms since the early creation of firearms as a means of stabilizing a firearm to reduce vibration, wavering, etc., and to improve accuracy. 
   In the past, shooters have used everything from large stationary objects such as rocks and tree branches to forked sticks, shooting slings, bipods and tripods. Early bipod and tripod supports typically were somewhat crude strands that generally were bulky, inconvenient and difficult to use and typically were not easily adjustable. In more recent times, bipod supports have been developed that are compact and relatively lightweight and are mountable to the forearm stock of a firearm, such as a rifle, to make the bipods portable with the firearm. Most conventional bipod supports include a pair of legs that can be pivoted from an up position adjacent the firearm stock, to a down position engaging a support surface, with the legs also being extensible to adjust the height of the support. 
   A problem with conventional bipods has been the ability of the bipod to mount to most firearms without requiring the use of special mounting tools and the machining or modification of the firearm stock to accommodate the bipod. Additionally, most bipods are not designed for quick and easy attachment and release of the bipod from the firearm stock. For example, U.S. Pat. No. 5,194,678 discloses a bipod assembly that includes legs that are pivotable independently of one another for ease of adjustment, but which is not easily attached/detached from the firearm. Other types of conventional bipods offer varying types of mountings that can be fitted to various types of rifles without requiring modification or machining of the rifle stock. Harris Engineering, Inc. manufactures a series of bipod mounts for use with a variety of different firearms. However, these bipod mounts do not provide for the quickly releasing an attached bipod support from the firearm. 
   One of the most popular bipods on the market has been the Parker-Hale bipod assembly. This bipod includes a pair of telescoping legs attached to a mounting frame, and a mounting block for mounting the bipod to the firearm. The mounting block of the Parker-Hale bipod is releasably attached to the mounting frame of the bipod to enable quick attachment/release of the legs of the bipod from the firearm. The problem with the Parker-Hale bipod is that to mount the bipod to a firearm, the forearm stock of the firearm generally must be modified to mount a track or slide therein, along which the mounting block is received to mount the bipod to the firearm. Such modifications generally are expensive and often must be done by specialty gunsmiths and can mar the finish of the firearm. 
   Military or police shooters using military or SWAT rifles often carrying special mounts known as MIL-STD-1913 “picatinny” rails under the rifle forearm; the picatinny rails are customarily used for mounting grenade launchers, lights or other accessories and so the rifles often weigh much more than the lighter sporting arms most shooters are used to carrying. Clamping objects to forearm mounted picatinny rails is usually a lengthy, cumbersome process requiring that the shooter juggle small parts in the field. 
   Accordingly, it can be seen that a need exists for a bipod mounting device for selectively attaching a bipod to a firearm adapted for use in military or SWAT situations, where the shooter may choose, for precision aiming, to have a stable support. Ideally, the attachment should not require extensive modification to the firearm such as machining of the forearm stock of the firearm. Preferably, a mounting device would also enable quick and easy attachment and detachment of the bipod (or other accessory) to the firearm. 
   SUMMARY OF THE INVENTION 
   The present invention comprises a mounting clamp assembly for mounting an accessory such as a bipod support to a mounting rail structure as are often affixed below the forearm stock of a firearm such as a military rifle. In an illustrative embodiment, the present invention is directed to use for mounting a Parker-Hale style of firearm bipod of the type including a mounting block with an integral clamp assembly to cover and attach to a picatinny rail affixed beneath the forearm stock of the firearm. The mounting block is releasably attachable to a bipod mounting frame by means of a transverse bolt or a similar fastening means. The bipod mounting frame includes a pair of extensible/retractable legs, each having a pair of telescoping sections to enable the height of the bipod to be adjustable as desired. 
   The bipod mounting device of the present invention generally comprises a clamp body with a mounting yoke that is adapted to slide over and receive the picatinny rail. The yoke is releaseably affixed to and hangs from the picatinny rail. The yoke includes a substantially rectangular base plate defining the central upper surface of a clamp body and includes a pair of parallel sidewalls extending upwardly therefrom. The base plate is a substantially flat plate having, in one embodiment, first and second rectangular elongate transverse openings or bores formed across the centerline of the rectangular base plate&#39;s central upper surface. In a preferred embodiment, first and second substantially rectangular upwardly movable bolts are slidably disposed within the first and second rectangular elongate transverse openings in the rectangular base plate&#39;s central upper surface and are controllable or actuable to project upwardly from the yoke base plate&#39;s central upper surface. 
   The yoke base plate sidewalls include inwardly facing v-shaped grooves and are spaced apart; the sidewalls are adapted to fit about and straddle the sides of the picatinny rail mounted to the forearm stock of the firearm, with the length of the rail being received between the side walls. The picatinny rail is a standard element of the military firearm and normally is used for attaching a variety of accessories including lights, grenade launchers and other devices. The clamp body&#39;s first and second transverse bolts, when raised and aligned with the transverse grooves of the picatinny rail, are received in the spaced transverse grooves of the rail to attach the yoke to the rail. 
   The bolts are actuated by turning an elongate control screw keyed to turn first and second eccentric rotating cam members within the clamp body and beneath the first and second bolts. Each cam preferably bears on a cam-following spring retaining block which includes first and second vertical through bores containing first and second biasing coil springs. Each bolt is preferably configured as a J shaped member with the cam and spring retaining block disposed within the interior contour of the bolt, such that the cam and spring retaining block can be rotated to urge the cam into an upwardly projecting position, or can be rotated into a position tending to force the bolt downwardly, to lower the bolt such that it does not project above the yoke base plate&#39;s central upper surface. 
   In use, the bolts are initially in the retracted position, such that neither bolt projects above the yoke base plate&#39;s central upper surface. Next, the shooter slides the clamp assembly&#39;s yoke over the picatinny rail of the firearm and places the clamp assembly in a selected aligned fore/aft position. Next, the clamp body&#39;s first and second transverse bolts are raised and are received in and constrained by the spaced transverse grooves of the rail to fixedly attach the yoke to the rail. 
   The resulting attachment of the clamp assembly to the forearm stock provides a quick and easy attachment of the bipod (or some other accessory) to the firearm and enables the clamp assembly to mount securely to the forearm stock of the firearm in a stable, secure selected position. This prevents the clamp assembly, and thus the accessory carried by the clamp (e.g., a bipod), from shifting fore and aft or wobbling during use. 
   With the clamp assembly securely mounted to the forearm stock of the firearm, the attached accessory (e.g., a bipod frame) is placed in locking engagement with the firearm. Optionally, a detachable sling loop can be provided with the clamp assembly for attachment of a rifle sling to the stock of the firearm. 
   Various objects, features and advantages of the present invention will become apparent to one skilled in the art upon a review of the following specification, when taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1   a - 1   d  illustrate a clamp assembly body showing the first and second transverse bolts in the raised, up, locked or closed position, in accordance with the present invention. 
       FIGS. 2   a - 2   e  illustrate the elongate control screw from the clamp assembly of  FIGS. 1   a - 1   d , in accordance with the present invention. 
       FIGS. 3   a - 3   e  illustrate a bolt from the clamp assembly of  FIGS. 1   a - 1   d , in accordance with the present invention. 
       FIGS. 4   a - 4   d  illustrate a cam following spring retaining block from the clamp assembly of  FIGS. 1   a - 1   d , in accordance with the present invention. 
       FIGS. 5   a - 5   c  illustrate an eccentric cam from the clamp assembly of  FIGS. 1   a - 1   d , in accordance with the present invention. 
       FIG. 6  is an exploded perspective view, in elevation, of the clamp assembly of  FIGS. 1   a - 1   d , in accordance with the present invention. 
       FIGS. 7   a - 7   d  illustrate the clamp assembly of  FIGS. 1   a - 1   d  with an attached bipod having adjustable length legs and ball in socket swiveling or self leveling feet, in accordance with the present invention. 
       FIG. 8  illustrates the clamp assembly of  FIGS. 1   a - 1   d  with the first and second bolts in the raised, up, locked or closed position, in accordance with the present invention. 
       FIG. 9  illustrates the clamp assembly of  FIGS. 1   a - 1   d  and  8  with the first and second bolts in the retracted, down, unlocked or open position, in accordance with the present invention. 
       FIG. 10  illustrates the clamp assembly with the first and second bolts in the retracted, down, unlocked or open position, and aligned for sliding over the free end of a mounting rail, in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
   Referring now to  FIGS. 1   a - 10  in which like numerals indicate like parts throughout the several views, the present invention comprises a clamp assembly  10  for mounting an accessory or support such as a bipod  12  to a firearm or other device or instrument. The clamp assembly  10  is generally is mounted to the forearm stock portion of the firearm via an elongate weaver style or picatinny arsenal style elongate mounting rail  50  as typically affixed below and carried on the front end of a rifle&#39;s forearm stock. 
   Mounting rail  50  can be any suitably strong and rigid elongate supporting structure but, in the above described illustrative embodiment, is a picatinny rail mounting structure (i.e., a MIL-STD-1913 picatinny rail) having a plurality of evenly spaced standard size transverse grooves (e.g.,  50 ,  54 , as best seen in  FIG. 10 ). Mounting rail  50  is preferably aligned in parallel with an instrument&#39;s operational axis (e.g., such as the central axis of a firearm&#39;s barrel), and terminates proximally in a proximal end and terminates distally in a distal end  56 . 
   As the Figures illustrate, the bipod  12  has first extendable leg  60  and second extendable leg  62  as described in co-owned U.S. Pat. Nos. 5,711,103 and 5,815,974, the entire disclosures of which are incorporated herein by reference. 
   As noted above, the present invention comprises a clamp assembly  10  for mounting an accessory support to a mounting rail structure. In the illustrated embodiment, the present invention is directed to use for mounting a Parker-Hale style of firearm bipod of the type including a mounting block with an integral clamp assembly to cover and attach to a picatinny rail affixed beneath the forearm stock of the firearm. The mounting block or clamp body is releasably attachable to an accessory such as bipod mounting frame  12  by means of a transverse bolt or a similar fastening means (as shown in  FIGS. 7   a - 7   d  and  FIG. 8 ). The bipod mounting frame preferably includes a pair of extensible/retractable legs, each having a pair of telescoping sections to enable the height of the bipod to be adjustable as desired. 
   The accessory mounting device of the present invention generally comprises a clamp body  10  with a body or mounting yoke  14  that is adapted to slide over and receive the opposing V shaped sides of picatinny rail  50 . The yoke  14  is releaseably affixed to and hangs from rail  50 . The yoke includes a substantially rectangular base plate surface  16  defining the central upper surface of a clamp body and includes a pair of parallel sidewalls  18 ,  20  extending upwardly therefrom. The base plate  16  is a substantially flat plate-like surface having, in one embodiment, first and second rectangular elongate transverse openings or bores  22 ,  24  formed across the centerline of the rectangular base plate&#39;s central upper surface (as best seen in  FIG. 6 ). In a preferred embodiment, first and second substantially identical rectangular upwardly movable bolts  26 ,  28  are slidably disposed within first and second substantially identical rectangular elongate transverse openings  22 ,  24  in the rectangular base plate&#39;s central upper surface  16  and are controllable or actuable to project upwardly from the yoke base plate&#39;s central upper surface (as shown in  FIGS. 1   a - 1   d  and  8 ). 
   The yoke base plate sidewalls  18 ,  20  include inwardly facing V-shaped grooves and are spaced apart; the sidewalls are adapted to slidably retain and straddle the V shaped sides of the picatinny rail mounted to the forearm stock of the firearm, with the length of the rail being received between the side walls. Mounting picatinny rail  50  is a standard element of the military firearm and normally is used for attaching a variety of accessories including lights, grenade launchers and other devices. The clamp body&#39;s first and second transverse bolts  26 ,  28 , when raised and aligned with the transverse grooves  52 ,  54  of the picatinny rail, are received in the spaced or alternate (e.g., third and fifth, counting from distal end  56 ) transverse grooves of the rail to affix yoke  14  to the rail, and in the embodiment illustrated, engage alternate rail grooves, leaving one rail groove not engaged between the bolts  26 ,  28 . The applicant has discovered that having a long clamping surface and engaging spaced apart grooves (e.g.,  52 ,  54 ) provides a more stable clamping action, and more reliable locking and unlocking, when used in harsh environments. 
   Bolts  26 ,  28  are actuated by turning an elongate control screw  30  around its own central axis. Control screw is keyed to turn first and second substantially identical eccentric rotating cam members  32  within the clamp body and beneath the first and second bolts  26 ,  28  (as best seen in the exploded view of  FIG. 6 ). 
   Referring now to  FIG. 5 , each cam  32  has at least one and preferably two cam lobes. In the embodiment illustrated, each cam  32  has a central key hole  70  dimensioned to closely fit onto the peripheral shape of the shaft of control screw  30 , and is in the illustrated embodiment, shaped as a 5.5 mm square. In the exemplary embodiment, a first cam lobe  72  is arrayed at approximately ninety degrees from a second cam lobe  74 , where both lobes provide a cam lobe lift of approximately 3.25 mm. First cam lobe  72  has a longer duration, gradually ramping up from a nominal radius of 5.5 mm to its maximum lift. First cam lobe  72  provides a lifting or locking action and bears against cam following block  36 , forcing cam following block  36  upwardly, and forcing the bolt upwardly as well. Second cam lobe  74  provides a positive lowering or unlocking action when bearing against the lower substantially planar portion of the J shaped lower portion of each bolt. Second cam lobe  74  has a shorter duration with abrupt, symmetrical shoulders. 
   As best seen in  FIGS. 4   a - 4   d , cam following block  36  has at least one and preferably two blind bores  38 ,  40  configured to receive coil biasing springs  42 ,  44  (best seen in  FIG. 6 ). Each cam following block  36  is fashioned as a rectangular box like shape having a length of approximately 8 mm, a width of 5.25 mm and a thickness of approximately 3 mm. The blind bores  38 ,  40  are preferably side by side and have a depth of 2 mm. Each cam following block&#39;s overall length is 9 mm, due to the axially projecting tongues  46 ,  48  dimensioned to slidably received in cooperating guiding grooves machined into the underside of each bolt  26 ,  28 . 
   Each bolt,  26 ,  28  has, as best seen in  FIG. 3   a - 3   e , a substantially planar upper surface  80  defined within four substantially perpendicular side walls  82 ,  84 ,  86 ,  88 , where two of the side walls correspond to the width of the bolt, 16 mm, and two correspond to the depth of the bolt, 5.25 mm, and together form a skirt-like support having a height of 7 mm. A “J” shaped actuating arm  90  depends from one of the short side walls  88  and extends downwardly below the bolt skirt depth. Actuating arm  90  is bent or radiussed in a gradual ninety degree bend to provide a bottom planar surface  92  extending substantially in parallel to bolt upper surface  80 . Actuating arm  90  is substantially rectangular in cross section, having a depth of 3 mm and a thickness of 2 mm. Each bolt,  26 ,  28  has, as best seen in  FIG. 3   a - 3   e  has a substantially rectangular recess defined within the sidewalls  82 - 88  to slidably receive cam following block  36 , and has opposing parallel grooves dimensioned to receive and cooperate with cam following block tongues  46 ,  48 , such that cam following block  36  can move up and down, compressing and releasing biasing force from captive biasing springs  42 ,  44  which are retained in the substantially rectangular recess within the bolt. 
   Each cam  32  preferably bears on a cam-following spring retaining block  36  which preferably includes first and second vertical blind bores  38 ,  40  containing first and second biasing coil springs  42 ,  44 . As best seen in  FIGS. 3   a - 3   e , each bolt&#39;s “J” shaped actuating arm partially encircles cam  32  and the spring retaining block  36  is also disposed within the interior contour of the bolt (see  FIG. 6 ). 
   Control screw  30  has a T-shaped distal handle  31  with an overall length of 22 mm and a width, in the handle&#39;s symmetrical extensions, of 4 mm, with rounded ends. The control screw distal end preferably also includes a slot and a hex socket for actuation by either a screw driver or a hexagonal section Allen™-style wrench. Control screw  30  preferably has a central shank portion having a key-shaped cross section adapted to carry and drive the first and second cams  32 . In the illustrated embodiment of  FIGS. 2   a - 2   e , the shank has a substantially square cross section, 5.5 mm on a side, with chamfered corners, terminating proximally in a threaded cylindrical end adapted to receive and retain a threaded nut fastener. 
   When control screw  30  is turned counterclockwise in its longitudinal bore within clamp yoke  14 , each cam  32  is rotated and its respective spring retaining block  36  is simultaneously urged up to simultaneously force both bolts into an upwardly projecting actuated or locked position (as in  FIG. 8 ). Control screw  30  has a T-shaped distal handle  31  which is preferably in a vertical orientation when the bolts are in an actuated or locked position (as best seen in  FIGS. 1   d  and  7   d ). 
   When control screw  30  is turned clockwise, by ninety degrees, in its longitudinal bore within clamp yoke  14 , each cam  32  is rotated into a position tending to simultaneously positively force the bolts downwardly by acting on bolt actuating arm  90 , at bottom planar surface  92  to lower the bolts  26 ,  28  such that the bolt&#39;s upper surfaces  80  do not project above the yoke base plate&#39;s central upper surface  16  (as in  FIG. 9 ). Control screw  30  has a T-shaped distal handle  31  which is preferably in a horizontal orientation when the bolts are in the unlocked, down or retracted position (as best seen in  FIGS. 1   d  and  7   d ). 
   In use, the bolts  26 ,  28  are initially in the unlocked, down or retracted position, such that neither bolt projects above the yoke base plate&#39;s central upper surface  16  (as in  FIG. 9 ). To install the clamp assembly  10  on support rail  50 , as shown in  FIG. 10 , the user or shooter slides the clamp assembly&#39;s yoke  14  over the free distal or proximal end  56  of rail  50  and places the clamp assembly  10  in a selected aligned fore/aft position. Next, the clamp assembly&#39;s control screw  30  is rotated or twisted by grasping the control screw&#39;s T-shaped handle segment  31 , thereby simultaneously rotating cams  32 ,  34  and forcing first and second transverse bolts  26 ,  28  to the raised, closed or locked position, whereupon bolts  26 ,  28  are received in and constrained by the spaced apart transverse grooves  52 ,  54  of support rail  50  to fixedly attach yoke  14  to rail  50 . 
   Alternatively, support rail  50  could have a line of apertures (not shown) sized to receive at least one bolt, and the yoke sidewalls could be dimensioned to slidably partially encircle the cross-sectional periphery of a support having a different cross section than the rail of the illustrative embodiment. 
   The resulting attachment of the clamp assembly  10  to the forearm stock provides a quick and easy attachment of the bipod (or some other accessory) to the firearm (or some other instrument) and enables the clamp assembly to mount securely to the forearm stock of the firearm in a stable, secure selected position. This prevents the clamp assembly  10 , and thus the accessory carried by the clamp (e.g., bipod  12 ), from shifting fore and aft or wobbling during use. 
   With clamp assembly  10  securely mounted to the forearm stock of the firearm, the attached accessory (e.g., bipod  12 ) is placed in locking engagement with the firearm. Optionally, a detachable sling loop (not shown) can be provided with the clamp assembly for attachment of a rifle sling to the stock of the firearm. 
   As noted above, mounting yoke  14  defines a substantially U-shaped block having inwardly facing opposing V-shaped grooves in vertical sidewalls  18 ,  20  and is preferably formed from a hardened metal such as steel or similar durable, high-strength material. The side walls  37  and  38  are spaced apart at a distance sufficient to slidably receive the rail and limit lateral movement. Bolts  26 ,  28  function as transverse fasteners and, when in the rail&#39;s transverse grooves  52 ,  54 , provide substantially square cross section elongate retaining members that are received through clamp body bores  22 ,  24  in the base plate surface  16  of mounting yoke  14  and through the aligned transverse grooves of the picatinny rail, thereby limiting fore and aft movement of clamp assembly axially along the axis of the supporting picatinny rail. 
   It will be appreciated that  FIG. 6  illustrates an exploded perspective view of a clamp assembly  10  embodying the principles of this invention. Yoke  14  has mirror image upstanding sides or sidewalls  18 ,  20  that project from base plate surface  16 , also referred to as a bight portion or floor. 
   In use, to quickly attach the clamp assembly, the user first twists the control screw handle  31  to lower the bolts  26 ,  28  and then slides yoke  14  over the proximal or distal end of the mounting rail (secured to the forearm stock) and slides yoke  14  into a selected fore/aft position, aligning a selected support rail transverse groove with bolts  26 ,  28 . The bolts may then be raised or locked into engagement with the receiving transverse grooves defined in the picatinny rail to secure the picatinny rail within the yoke  14 . To quickly and easily release the clamp assembly, the user then twists the control screw handle to lower the bolts  26 ,  28  into a disengaged or unlocked position and then slides yoke  14  over and beyond the proximal or distal end of the mounting rail. 
   If needed, a bipod  12  is received and mounted to the clamp body; the bipod legs can be folded into a raised non-operative position when not in use, and can quickly be lowered to an operative, ground engaging position when needed. 
   It will be understood that while the foregoing relates to a preferred embodiment of the present invention, various modifications, additions and changes may be made thereto without departing from the spirit and scope of the invention as set forth in the claims. 
   Further, it will be understood by those skilled in the art that while the present invention has been disclosed for use primarily with the Parker-Hale bipod assembly, the present invention also can be used for mounting the types of bipods having a bipod leg frame that is releasably mountable to a mounting block for a firearm.