Abstract:
A clamping device, preferably for use on a retractor support, has an upper clamp and a lower clamp. The clamps include a movable jaw and a fixed jaw pivotal between a locked configuration and an unlocked configuration which both locks the clamps in a shut configuration and fixes the angular position of the clamps relative to one another. A drawbar and cam act together to compress the upper and lower clamps into a clamping or locking position.

Description:
[0001]    This application claims the benefit of U.S. Provisional Application No. 60/293,057 filed May 23, 2001. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to surgical retractor support devices and, more particularly to a multi-position clamping mechanism for a surgical retractor.  
         BACKGROUND OF THE INVENTION  
         [0003]    In surgery that requires access to internal structures, retractors are often used to hold back tissue and expose the area in which the surgical operation is to be performed. A retractor typically includes a retractor blade and a retractor shaft upon which the retractor blade is mounted. The retractor is attached to a retractor support by a clamping device. The retractor support includes a rod which the retractor clamp can engage to connect the retractor to the retractor support.  
           [0004]    An essential feature of any retractor clamp is that the clamp allow the retractors to be conveniently positioned on the retractor support and be adjustable as necessary to achieve appropriate positioning with respect to the area of surgical operation.  
           [0005]    Various types of clamping devices have been proposed. Minnesota Scientific, Inc. is the assignee of U.S. Pat. Nos. 4,949,707, 5,020,195, 5,025,780, 5,242,240, 5,727,899, and 5,792,046, which are incorporated by reference. These patents relate to various improvements to the basic concept of holding two rod sections in an adjustable and fixable angular relationship relative to one another when locked in position. One of the rod sections is usually a retractor handle and the other is usually a rod section of a retractor support, which may be mounted to the operating table or other appropriate location.  
           [0006]    Although, these clamping devices are believed to operate satisfactorily (i.e., to clamp two rod sections in a specific angular relationship), a need exists to provide the ability for at least one of the two rod sections to “snap” into a loosely gripped position to allow for precise positioning off the rod relative to the clamp before “clamping” the clamp into a securely locked position which prevents either of the two rod sections from moving relative to one another.  
           [0007]    A need also exists to provide jaws for clamping members, which operate about pivot points to provide a scissors-like gripping action.  
           [0008]    Furthermore, although the frustro-conical section provided in U.S. Pat. No. 4,949,707 provides one way to provide a large amount of surface area to resist twisting of the clamping members relative to one another when locked, an improvement is needed to securely position the two clamping members relative to one another in a locked position.  
         SUMMARY OF THE INVENTION  
         [0009]    The retractor clamp preferably includes a drawbar extending at least partially through two clamping members which are rotatable relative to one another. The clamping members are comprised of a stationary jaw and a jaw movable about respective pivot points upon activation of a connected lever arm. The draw bar has an opening at its distal end for holding a dowel. The dowel fits within a cam nut such that when the draw bar is turned the cam activates the lever arms locking the clamps in a closed position.  
           [0010]    A spring located in the lower clamping member biases the moveable arms such that the first and second jaws are biased to “snap” about an inserted rod section.  
           [0011]    The two clamping members are separated by a lock bushing having a top disc and a bottom disc. The lock bushing has a preload spring between the top and lower disc. When the cam is not activated the preload spring prevents the top bushing and the lower bushing from engaging. This allows the two clamping members to rotate freely with respect to one another  
           [0012]    Additionally, the lock bushing top and bottom discs adjoin one another along cooperating serrations. The cooperating serrations engage one another when the drawbar is turned sufficiently to activate the cam, thereby locking the first and second clamping members in a fixed angular relationship relative to one another. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    The particular features and advantages of the invention as well as other objects will become apparent from the following description taken in connection with the accompanying drawings in which:  
         [0014]    [0014]FIG. 1 is an exploded perspective view of the clamp of the preferred embodiment of the present invention;  
         [0015]    [0015]FIG. 2 is a perspective view of the clamp of FIG. 1;  
         [0016]    [0016]FIG. 3 a  is a perspective view of a cam nut shown in FIG. 1;  
         [0017]    [0017]FIG. 3 b  is a side-on view of the cam nut of FIG. 3 a;    
         [0018]    [0018]FIG. 4 a  is a cross-section view of a portion of the lower clamp as shown along the line A-A in FIG. 1;  
         [0019]    [0019]FIG. 4 b  is a cross-section view taken along line B-B of the lower clamp in FIG. 1; and  
         [0020]    [0020]FIG. 5 is a perspective view of the lock bushing disc.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0021]    The retractor clamp  10  of FIGS.  1 - 4  may be utilized as a replacement for or instead of the clamp illustrated in FIG. 1 of U.S. Pat. No. 5,020,195. However, the clamp  10  of the present preferred embodiment is believed to improve on the basic design of that prior art retractor clamp and others.  
         [0022]    The clamp  10  of FIG. 1 is comprised of two clamping members  45 ,  90  with each having at least one moveable jaw member  55 ,  100 , respectively. The moveable jaw members  55 ,  100  preferably rotate about respective pivots  56 ,  101  when forces are exerted on lever arms  57 ,  102  which are located opposite the pivot points  56 ,  101  at moveable jaws  55 ,  100 . The moveable jaw members  55 ,  110  are pivotably connected to the clamping members  45 ,  90  by upper clamp dowel  50  and lower clamp dowel  95 , respectively.  
         [0023]    In the preferred embodiment, each of the moveable jaws  55 ,  100  cooperates with a second jaw member  60 ,  105 , which is preferably a fixed, or non-moving jaw member. In a more preferred embodiment, the fixed jaw members  60 ,  105  are of unitary construction with a significant portion of the upper and lower clamps  45 ,  90  respectively. The fixed jaw members  60 ,  105  have a gripping surface  61  (obscured from view on jaw member  60 ) and  106  which cooperate with gripping surfaces  58  and (obscured from view on jaw  100 ) of the moveable jaw members  55 ,  100  to hold rod sections such as a shaft of a retractor and a rod section of a retractor support. The jaw faces such as gripping surfaces  106 ,  58  are preferably curved to aid in holding the rod sections once they are in place.  
         [0024]    The clamping members  45 ,  90  are separated by a bushing such as lock bushing  64 . The lock bushing  64  consists of top lock  65  and lower lock  70 . The locks  65 ,  70  illustrated as disks are preferably constructed with serrated interfaces  71 , as best seen in FIG. 5, which cooperate with one another to maintain the upper clamp  45  in a fixed radial position relative to the lower clamp  90  when the clamping members  45 ,  90  are locked, at least angularly, relative to one another. The serrated interfaces  66 ,  71  in the preferred embodiment resemble a starburst type shape characterized by radially extending ridges. The upper and lower discs  65 ,  70  are separated by pre-load spring  75 . The pre-load swing  75  keeps the serrated interfaces  71  from contact when the clamping members  45 ,  90  are in an unlocked or release position. The spring  75  therefore assists in the free rotation of the clamping members  45 ,  90 .  
         [0025]    In the preferred embodiment, a drawbar  20  is utilized to operate the moveable jaws  55 ,  100  and to lock the upper and lower clamping members  45 ,  90  in a fixed angular relationship relative to one another. The drawbar  20  extends through bores  46 ,  91  in the clamping members  45 ,  90 . The drawbar  20  also extends through channels  59 ,  104  in lever arms  57 ,  102 .  
         [0026]    The drawbar  20  may be rotated within clamping members  45 ,  90  by handle  15 . The handle  15  or gripping surface is positioned to receive handle ball  25  as shown in FIG. 2. Handle spring  30  biases the handle ball into the handle  15 . When handle  15  is raised it pivots around handle dowel  35  while maintaining contact with ball  25 . The handle ball  25  is preferably received within a recess (obscured from view) in base  16  of handle  15  when the handle  15  is pivoted to be substantially perpendicular to the drawbar  20 . When the handle  15  is released the handle spring  30  may assist to bias the handle to a closed position as shown in FIG. 2.  
         [0027]    The drawbar  20  has drawbar head  21  with lip  22 , which rests on washer  23 , such as a friction washer. The drawbar head  21  when turned rotates on the washer  23 , which abuts lever arm  57 . The turning of the drawbar drives the drawbar head  21  downward applying sufficient downward forces on the lever arm  57  with the lip  22  to actuate a closed or clamping position as will be explained in further detail below.  
         [0028]    The drawbar  20  is secured within the clamping members  45 ,  90  by a cam illustrated as a cam nut  85 , best seen in FIG. 3 a . Cam nut  85  is engineered to receive cam nut dowel  86 , which extends from the hole  23  in the distal end  24  of the drawbar shaft  19 . The cam nut dowel  86  is positioned to fit within the cam nut  85  such that when the drawbar  20  is turned the nut dowel  86  moves relative to the cam nut  85 .  
         [0029]    The shape of the cam nut  85  may be any shape that allows it to be housed within the lower clamp  90  so that the cam nut  85  preferably will not rotate when the drawbar  20  is rotated. Referring to FIG. 3 a , the cam nut  85  is illustrated upside down in a preferred embodiment showing three sides of a hexagonal nut base  87  with each side having a turret  84 . FIG. 3 a  further illustrates the cam portions  81 ,  82 . FIG. 3 b  shows the cam nut  85  as it is placed in the retractor clamp  10 . Dowel channel  89  holds the cam nut dowel  86  and separates a first cam ramp  81  and a second cam ramp  82 . When the drawbar  20  is turned the cam nut dowel  86  preferably rotates up both cam ramps  81 ,  82 . As shown in FIG. 3 b  the cam dowel  86  can only turn in one direction, in this case clockwise, however the cam nut  85  can be constructed to turn in the opposite direction with equal effect. If the article to be gripped by the clamping members has a diameter too small to be gripped by the retractor clamp  10  the cam nut dowel  86  may ride over the cam ramps  81 ,  82  and fall back into the dowel channel  89 .  
         [0030]    Referring back to FIG. 1, the cam nut  85  is supported from below by cam nut dowel  86  and is prevented from upward vertical movement by the compression spring  80 , which presses against the cam nut  85  and the lever arm  102 . The cam nut  85  is prevented from rotating or lateral movement by cam nut housing  83  located in the interior of lower clamp  90  as shown in FIG. 4 a . The hexagonal shape of the cam nut housing  83  of the lower clamp  91  is shown in this figure. The shape of the cam nut housing  83  has been designed to accept the cam nut turrets  84  of the cam nut  85  thereby preventing the cam nut  85  from rotating in the lower clamp bore  91 .  
         [0031]    The compression spring  80  positioned between the cam nut  85  and lower clamp moving jaw  100  preferably performs the dual function of biasing the lever arm  102  to a static clamping position thereby placing the clamp  90  in a shut configuration, but not a locked configuration, i.e., when in an unlocked configuration, and biasing the cam nut  85  to the cam dowel  86  such that when the cam dowel  86  is turned a predetermined amount, the spring  80  is compressed further tightening the upper and lower clamps  45 ,  90  into a locked configuration. Accordingly, when inserting a rod to be fixed by the lower clamp  90 , the rod may be pushed into the clamping member  90  so that it “snaps” into position even while the retractor clamp  10  is in an unlocked configuration loading surfaces  120 ,  122  on jaws  55 ,  105  may also be present on jaws  60 ,  100  to assist in spreading the jaws  55 ,  60  and  100 ,  105  upon insertion of a rod (i.e., the curved surface of the rod would spread the jaws apart until the diameter was reached, and the jaws would come back together about the rod.) The lower clamp moving jaw  100  is biased downward by the spring  80  since the spring  80  pushes upward on the lever arm  102  forcing moving jaw  100  downward toward the fixed jaw  105 . The force exerted by the compression spring  80  is preferably sufficient to secure the retractor clamp  10  to a rod.  
         [0032]    After the lower clamp  90  has been placed into position the drawbar  19  can be turned which turns the cam dowel  86 . This movement causes the dowel  86  to ride up the cam ramps  81 ,  82  compressing spring  80  and moving or exerting upward force on the lever arm  102  and places the clamp  90  in a locked configuration. The upward force on lever arm  102  provides additional grip to further secure a rod section.  
         [0033]    In order to lock the upper clamp  45  about a rod section the drawbar  20  may be rotated, such as by handle  15  by the same rotation that locks clamp  90 . In the preferred embodiment, less than 270 degrees, and less than 180 degrees of rotation have each been found satisfactory to lock the clamping members  45 ,  90  about a rod section. Once again the rotating action of the handle  15  causes the cam nut dowel  86  to turn and ride up the cam ramps  81 ,  82 . This motion pulls the draw bar head  21  down and forces the lip  22  to place pressure on the friction washer  40 , which in turn pushes down on lever arm  57  into a locked configuration. Lever arm  57  pushes moving jaw  55  upward and toward the fixed jaw  60  until the upper clamp  45  has secured the inserted rod section.  
         [0034]    Another effect associated with the downward force applied by the drawbar head  21  and/or action of the drawbar  20  with the cam nut  85  is the compression of the pre-load spring  75  in lock bushing  64 . This forces the serrated disc faces  71 ,  66  to contact one another and cooperate with one another to maintain the upper clamp  45  in a fixed radial position relative to the lower clamp  90  in a locked configuration. Rotation can be reestablished by turning the drawbar  19  in the opposite direction riding the cam dowel  86  back down the cam ramps  88 . While a single drawbar  20  and cam nut  85  are utilized to lock and unlock the clamps  45 ,  90  and the bushing  64 , a plurality of similar or dissimilar mechanisms could be utilized in other embodiments.  
         [0035]    Numerous alterations of the structure herein disclosed will suggest themselves to those skilled in the art. However, it is to be understood that the present disclosure relates to the preferred embodiment of the invention, which is for purposes of illustration only and not to be construed as a limitation of the invention. All such modifications, which do not depart from the spirit of the invention, are intended to be included within the scope of the appended claims.