Abstract:
An improved clamping device and method for a weapon accessory rail of a type having an elongate mounting structure of generally T-shaped cross-sectional shape, such as a Picatinny mounting rail, is provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. provisional application No. 61/653,755, filed May 31, 2012. The aforementioned application is incorporated herein by reference in its entirety. 
     BACKGROUND 
     The present disclosure relates to a clamp device for attachment to firearm mounting rail system such as a so-called Picatinny or floating rail structure (e.g., as per standard MIL-STD-1913) of a type commonly attached to a military firearms for attaching optical scopes, thermal or laser sights, tactical flashlights, vertically extending handgrips, or other weapon-mounted accessories. 
     SUMMARY 
     A clamping device for a weapon accessory rail of a type having an elongate mounting structure of generally T-shaped cross-sectional shape comprises a mounting base having a first clamping surface engaging a mounting surface of the mounting structure, an outward facing surface opposite the first clamping surface for attaching an accessory device thereto, and a hook disposed on a first transverse side of the mounting surface. The hook is configured to engage a first transverse side of the mounting structure. A pressure plate is slidable with respect to the mounting base and is received between first and second arms. The first and second arms are axially spaced apart and extend from the mounting surface on a second transverse side of the mounting surface opposite the first transverse side of the mounting surface. A cam member has a lever attached to a cam body, the cam body pivotally mounted between the first and second arms. The cam body bears against the pressure plate to cause sliding movement of the pressure plate in response to pivoting movement of the lever. A locking tab is slidably attached to the pressure plate, and is slidable between a locked position and an unlocked position. The locking tab has a lip engaging the cam member to prevent pivoting movement of the cam body out of a clamped position when the locking tab is in the locked position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating preferred embodiments and are not to be construed as limiting the invention. 
         FIG. 1  is an isometric view of an exemplary embodiment rail clamp attached to a Picatinny rail. 
         FIGS. 2A-2D  are end views of the embodiment appearing in  FIG. 1 , and illustrate the manner of removing and attaching the rail clamp to the mounting rail. 
         FIG. 3  is an enlarged top, isometric view of the rail clamp embodiment appearing in  FIG. 1 , shown in the locked position. 
         FIG. 4  is an enlarged bottom, isometric view of the rail clamp embodiment appearing in  FIG. 1  in the locked position. 
         FIG. 5  is a generally exterior facing exploded view of the clamp embodiment appearing in  FIG. 1 . 
         FIG. 6  is a generally interior facing exploded view of the clamp embodiment appearing in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIGS. 1 ,  2 A- 2 D, and  3 - 6 , an exemplary embodiment clamp in accordance with the present disclosure is shown, designated generally as  100 , for removable attachment to a rail system  200  having one or more elongate mounting members  210 . The rail clamp  100  includes a mounting base  110  and a movable pressure plate  112 . The mounting base  110  includes an upper (in the orientation shown in  FIG. 1 ) surface  114  having one or more apertures  116 , which are preferably tapped or internally threaded openings for securing an accessory or device (not shown) to the surface  114  for removable mounting on the weapon rail interface  200  using the clamping member  100 . 
     The mounting base  110  defines an axial channel  118  defined by a first inner surface  120  opposite the upper surface  114  for engaging the mounting member  210  when the unit  100  is attached to a weapon rail mounting system  200 . The axial channel  118  is also defined by a second inner surface  122  for engaging a distal inclined surface  212   a  of the mounting member  210 , which is in aligned and facing contacting relation when the unit  100  is attached to the mounting member  210 . 
     In the depicted embodiment, a protruding member  124  may be provided on the inner surface  120 , e.g., integrally formed or separately formed and attached via a threaded fastener, adhesive, or other fastening means. The protruding member  124  is sized to be received within a selected one of the grooves  214  to prevent axial movement of the clamping member  100  relative to the rail mounting member  210 , e.g., due to recoil of the firearm when a round is fired. 
     The mounting base  110  includes a pair of arms  126 , which are spaced apart in the axial direction and extend generally downward on the opposite transverse side of the mounting surface  114  as the second inner surface  122 . The pressure plate  112  is slidably received between the arms  126 , and is slidable in a direction orthogonal to a proximal inclined surface  212   b  of the mounting member  210 . The pressure plate  112  includes a first, rail-engaging surface  128 , which engages the proximal inclined surface  212   b  in aligned and facing contacting relation when the unit  100  is attached to a mounting member  210 . The pressure plate  112  also includes a cam-engaging surface  132  opposite the rail engaging surface  128 . 
     The pressure plate  112  includes a projection  132  having a pair of rails  134  defining a dovetail slot  136 . A sliding, locking tab  138  is slidably received within the dovetail slot  136 . Although the slot  136  and tab  138  are shown as having complimentary generally female and male dovetail shapes, respectively, it will be recognized that other geometries could be used in place of the dovetail slot, such as a T-slot, or any other complimentary geometric shape that provide for sliding retention of the tab  138 . 
     Pressure plate retention pins  140  are received in openings  142  formed on the pressure plate. The pins  140  run along the interior surface of the arms  126  and prevent the pressure plate  112  from being disengaged from the unit  100 , while allowing sliding movement of the pressure plate  112  relative to the arms  126  as it follows the cam surface, as will be described in greater detail below. 
     A pair of channels  144  is formed in the projection  132  between the rails  134 . A spring  144  is captured within each channel  140 . A pair of protrusions  148  is formed on the interior facing surface of the tab  138 , aligned with and received in the channels  144 . In operation, the springs  146  bear against the protrusions  148 , urging the locking tab  138  generally downward (in the orientation shown in  FIG. 5 ) and toward the locked position as shown in  FIG. 1 . The springs  146  may be coil springs, leaf springs or other resilient members. As will be discussed in greater detail below, manually sliding the tab  138  generally upward compresses the springs  146  and allows the unit  100  to be unlocked. A tab retention pin  150  retains the sliding tab  138  within the channel  136 . The pin  150  extends through an opening  152  on the locking tab  138  and runs in an elongate opening  154  on the projection  132  to limit the extent of sliding movement. 
     A pressure plate height adjustment member  160  includes a bearing surface  162  abutting the surface  130  of the pressure plate. Extending from the height adjustment member opposite the bearing surface  162  is an externally threaded rod  164 . An internally threaded nut  166 , which is complimentary with the threaded rod  164 , is rotatably received on the threaded rod  164 . 
     A cam member  170  is rotatably secured to the mounting base  110 . A pivot pin  172  passes through openings  174  in the arms  126  of the base member  110  and an opening  176  in the cam member  170  to allow the cam member  170  to pivot relative to the base member  110 . The opening  176  is eccentrically positioned in the cam body  176 . The cam member  170  includes tabs  178   a  and  178   b  to allow the user to manually rotate the cam member  170 . A cam body  180  is disposed between the tabs  178   a  and  178   b.    
     An upper recess  182  is formed in the upper (in the orientation shown in  FIG. 6 ) surface of the cam member  170 . The height adjustment member  160  is received within the upper recess  182  and the threaded rod  164  extends through openings  184  and  186 . A central recess  188  is formed in the interior of the cam member  170 . The nut  166  is received within the central recess  188 . The nut  166  is rotatably received on the threaded rod  164  and an aperture  190  is provided to allow the user access to manually rotate the nut  164 . 
     In this manner, rotation of the nut  166  in one direction causes the threaded rod to advance in one direction relative to the axis of the threaded rod  164 , thus moving the height adjustment member  160  toward the pressure plate surface  130 . Rotation of the nut  166  in the other direction causes the threaded rod  164  to axially retract, thus moving the height adjustment member  160  to move away from the pressure plate surface  130 . By adjusting the position of the height adjustment member  160 , the clamping pressure exerted when the unit  100  is secured to the rail member  210  can be adjusted. The threaded rod extends in a direction orthogonal to the proximal inclined surface  212   b , thereby exerting a clamping pressure in a direction orthogonal to the surface  212   b . This allows the unit  100  to better maintain its original orientation upon removal and reattachment than prior art devices that employ a transverse clamping force. 
     The cam body  180  of the cam member  170  has a generally curved surface and provides a camming action when the cam member  170  is rotated about the pivot axis  192 , defined by the pivot pin  172 , relative to the mount body  110 , i.e., from the open position (see  FIG. 2C ) to the closed position (see  FIG. 2A ). The bearing surface  162  is likewise curved or tapered (e.g., in cross-sectional shape) and cooperates with the curved surface of the cam body  180  to define a cam surface of the cam body  180 . The cam body  180  is eccentrically shaped (e.g., by off-center placement of the pivot axis  192  and pivot pin  172 ) such that the distance between the pivot axis  192  and the portion of the cam surface facing the surface  130  of the pressure plate  112  is greater when the cam member  170  is rotated to the closed position and less when the cam member  170  is rotated to the open position. 
     In operation, when the cam member  170  is pivoted to the closed position (see  FIG. 2A ), the springs  146  urge the tab  138  downward (in the orientation shown) such that a lip portion  194  of the tab  138  extends over the cam member  170 , thereby preventing the operator from inadvertently rotating the cam member  170 . In the event it is desired to remove the unit  100  from the rail member  210 , the tab  138  is manually slid upward against the bias of the springs  146  until the lip  194  is clear of the cam member  170  (see  FIG. 2B ). A grooved or knurled surface or other high friction surface may be provided in the exterior facing surface of the tab  138  to assist the operator in sliding the tab  138 . 
     After the tab  138  is moved to the unlocked position wherein the lip  194  is clear of the cam member  170 , the cam member  170  is manually pivoted from the closed position to the open position using the tabs  178   a  and/or  178   b , at which time the unit  100  and any attached accessory device can be removed from the rail member  210 . As can be seen in  FIG. 4 , the edges of the tabs  178   a  and/or  178   b  may protrude in the axial direction beyond the edges of the arms  126  to assist the user in manual rotation the cam member  170  after the tab  138  has been slid to the unlocked position. 
     To attach the unit  100 , the above process is reversed. In the event adjustments need to be made to the clamping pressure exerted by the cam body  180  and the pressure plate  112 , the nut  166 , which is accessible through the window  190  when the unit  100  is removed from the rail member  210 , is rotated in the desired direction to selectively make fine adjustments to the clamping pressure. 
     The invention has been described with reference to the preferred embodiments. Modifications and alterations will occur to others upon a reading and understanding of the preceding disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.