Abstract:
An adjustable surgical retractor clamping mechanism for attaching mechanism to an operating table. The mechanism includes an upper jaw, lower jaw, a drive member, an adjustable frame support post and a releasable clamp for adjusting the height of the surgical retracting frame. The upper portion of the lower jaw has a plurality of slots cut into the sidewalls of upper jaw to form at least one flexible finger. The clamp is in close sliding relationship to the upper portion of lower jaw member. The clamp includes a cam lever. Movement of the cam lever to its closed position compresses the clamp causing the flexible fingers to grip the adjustable post locking its longitudinal movement. Rotation of the cam lever to the open position releases the compressive force on the clamp, unlocking the adjustable post allowing the post to be longitudinally adjusted relative to the clamping mechanism.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a divisional of U.S. application Ser. No. 12/466,489, filed May 15, 2009, now pending, which makes reference to, claims priority to and claims benefit from U.S. Provisional Patent Application Ser. No. 61/053,472, entitled “Adjustable Rail Clamp” and filed on May 15, 2008. 
     
    
     FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    [Not Applicable] 
       MICROFICHE/COPYRIGHT REFERENCE   
       [0003]    [Not Applicable] 
       BACKGROUND OF THE INVENTION 
       [0004]    The present invention relates to surgical apparatus for retracting anatomy to provide exposure of the operative site, and more particularly relates to a retraction apparatus that is sturdy, adjustable, and conducive to thorough sterilization. 
         [0005]    During surgical procedures, a surgeon will typically make an incision in a patient to access the sites of interest, such as internal organs and bone structures, for a particular procedure. A surgical retractor system is typically utilized to maintain clear access to the site of interest. Retractors are designed to hold back the anatomy in the immediate area of the operative site to enable a surgeon to have both an optimal view of the site and a sufficiently open area within which to work. 
         [0006]    The usefulness of any retractor device is necessarily limited by the number of ways that the retractor can be positioned with respect to the retracted anatomy as well as the ease with which the surgeon can adjust the relative position of the retractor both before and during surgery. The less obstructive and more versatile a retractor device is, the more desirable it becomes for use in the above-described manner. Thus, variance in types of surgery and patient size necessitates surgical retractor systems that are adjustable. In addition, equipment sterilization requirements call for a device that can be thoroughly cleansed by conventional means in a safe and easy manner. 
         [0007]    A surgical refractor system typically consists of a rail clamp, a frame connected to the rail clamp, and retractor blades that are clamped to the frame. The rail clamp is commonly secured to an operating table and provides a fixed and sturdy support for the frame and the retractor blades. Each of the components in a typical surgical retractor system is conventionally made of stainless steel, although, as disclosed in U.S. Pat. No. 6,033,363, parts of the system may be made from a nonconductive material. The reason that stainless steel is generally used is that stainless steel is easily sterilized. As would be expected, before any use of the surgical retractor system can be made during a surgical procedure, the system must be thoroughly sterilized for the protection of the patient. This sterilization is performed in the standard methods well known in the art. 
         [0008]    Often, a surgical retractor system frame includes one or more posts, each connected to the operating table by a rail clamp. Typically, some form of support structure for supporting retractor blades is connected to the post(s) by clamps. During surgical procedures, it is preferable that the surgical retractor system frame be adjustable to quickly position the retractor in a precise position. Prior art support structures generally repositioned the height of the surgical retractor by positioning the clamp connecting the surgical retractor to the post into a non-clamping position. With the clamp in a non-clamping position, the vertical position of the surgical retractor can then be repositioned into a new position. The surgical retractor is then secured to the post be placing the clamp in the clamping position. This procedure may add additional time to the surgical procedure, require additional personnel to perform the vertical adjustment and cause unneeded inconvenience to the surgical personnel. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    The system includes an adjustable clamp for clamping the system to an operating table, a post supporting member, and a frame which includes extension arms and refractor blades. A releasable locking mechanism is provided to releasably adjust the height of the retractor frame for quick and easy adjustment. 
         [0010]    In accordance with one aspect of the technology, the system comprises a clamping mechanism including a lower jaw, upper jaw and a jaw drive member to adjust the upper and lower jaws to fasten the system to a surgical operating table. A post frame member is located in the inner space of the lower jaw member. In addition, the device includes a locking device to releasably adjust the position of the post frame support member in relation to the clamping mechanism. The locking device is comprised of an outer sleeve slidably placed over the upper portion of the lower jaw member. Located in between the sleeve and the lower jaw member are a plurality of curved surface members. The sleeve has an internal circumferential shoulder to urge the curved surface members into sockets in lower jaw and grooved spaces that allow the curved members to partially retract from engagement of the sockets in the lower jaw. The sockets in the lower jaw are of such a dimension that part of the curved surface members is allowed to partially protrude into the lower jaw inner space. The post frame member has spaced circumferential grooves which are engaged and disengaged by the partially protruding curved surface members as the sleeve is positioned to engage or disengage the curved surface members. 
         [0011]    Another aspect of the technology provides a reversible ratchet assembly engaged on the jaw drive member through a plurality of ratchet gear teeth on the jaw drive member. The ratchet assembly comprises a handle with a ratchet head on the handle; the ratchet head includes a pivotal pawl, a compression spring, and a ball. The pivotal pawl is movable between a first position and a second position. Movement of the pivotal pawl to the first position causes the pawl to engage the ratchet gear teeth on the jaw drive member allowing for a ratcheting rotation of the jaw drive member in a first direction. Movement of the pivotal pawl to the second position causes the pawl to engage the ratchet gear teeth on the jaw drive member allowing for a ratcheting rotation of the jaw drive member in a second direction. 
         [0012]    A further embodiment of the present technology provides for an alternative locking device to releasably adjust the position of the post frame support member in relation to the clamping mechanism. The alternative locking device comprises a clamp apparatus that is operatively attached to the upper portion of the lower jaw member which contains a plurality of slots. The clamping apparatus includes a clamp and a cam member that is attached to the clamp through a shaft member. The operation of the cam member urges the clamp between an unclamped position and a clamped position. In the clamped position, the clamp closes around the slotted portion of the lower jaw member and compresses the upper portion of the lower jaw member to engage the adjustable post frame support member and prevent the movement of the adjustable post frame support member. In the unclamped position, the absence of compression of the slotted portion allows the slotted portion of the lower jaw member to return to its original position thus allowing the unlocking of the post frame support member. 
     
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
         [0013]      FIG. 1  is a perspective view of a surgical retractor system. 
           [0014]      FIG. 2  is an elevated view of a rail clamp assembly with a quick release slide lock for quick height adjustment of support post. 
           [0015]      FIG. 3  is an illustration of an upper jaw member of the rail clamp illustrated in  FIG. 2 . 
           [0016]      FIGS. 3A and 3B  are top and bottom views of the upper jaw member. 
           [0017]      FIG. 4  is a cross sectional view of a jaw drive member of the rail clamp illustrated in  FIG. 2 . 
           [0018]      FIG. 4A  is a top view of the jaw drive member. 
           [0019]      FIGS. 5A ,  5 B, and  5 C are top and side views of the handle portion of jaw drive member of  FIG. 4 . 
           [0020]      FIG. 6  is a side view of the lower jaw member of the rail clamp of  FIG. 2 . 
           [0021]      FIG. 7  is a side view of one embodiment of a vertical support post. 
           [0022]      FIG. 8  is a cross section view of one aspect of the slide lock assembly. 
           [0023]      FIG. 9  is a cross sectional view of a jaw drive member of the rail with ratchet teeth. 
           [0024]      FIG. 10  is a cross sectional side view of the ratchet assembly. 
           [0025]      FIG. 11  is a cut away top view of the ratchet assembly cooperatively engaged on the ratchet teeth of the jaw drive member. 
           [0026]      FIG. 12  is a side view of the lower jaw member of the rail clamp with slotted upper portion. 
           [0027]      FIG. 13  is an elevated view of a rail clamp assembly with a cam tightened clamp locking device for quick height adjustment of support post. 
           [0028]      FIG. 14  is a side view of the cam tightened clamp locking device. 
           [0029]      FIG. 15  is a top view of the cam tightened clamp locking device. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    As shown in  FIG. 1 , a surgical retraction system  10  includes an adjustable rail clamp  12  which is securable to a horizontal rail  15  of a conventional operating table (not shown). An adjustable post  17  extends vertically from the adjustable rail clamp assembly  12  to provide support for a cross bar  18  which in turn provides support for a pair of extension arms  19 ,  20 . The cross bar  18  is secured to the adjustable the adjustable post  17  by a universal joint clamp  21 . Extension arms  19 ,  20  are respectively secured to the cross bar  18  by a pair of universal joint clamps  22 ,  24 . Additional joint clamps  26 ,  28  may be disposed along the extension arms  19 ,  20  for rigidly securing any number of retractor blades  34 ,  36  to the extension arms  19 ,  20 . As will suggest itself, the extension arm  19  can also be secured directly to the adjustable the adjustable post  17  by a universal joint clamp. The adjustable post  17  may be adjusted vertically through a slide locking mechanism  140 . 
         [0031]    Each retractor blade  34 ,  36  may include a blade portion  42  and a retractor arm  44 . The blade portion  42  preferably extends downwardly into an incision  46  made by a surgeon. The blade portion  42  may be used to retract anatomy to make the incision  46  accessible to the surgeon. 
         [0032]    As is shown in  FIG. 2 , the adjustable rail clamp assembly  12  preferably is formed from a lower jaw member  58 , an upper jaw member  60 , and a jaw drive member  62 . The adjustable rail clamp assembly components  58 ,  60 ,  62  are associated with the adjustable post  17  such that the adjustable post  17  may be slidably inserted into lower the internal space  101  of lower jaw member  58 . The slide locking mechanism  140  may be slidably secured to the upper portion  100  of the lower jaw member  58  by snap rings  144 ,  147 . 
         [0033]    As can be seen in  FIG. 2 , the upper jaw member  60  can be positioned over the lower jaw member  58 . The jaw drive member  62  can then be rotabably mounted to the upper jaw member  60 . The adjustable post  17  can then be inserted into a space  101  of the jaw drive member  62 . The adjustable post  17  extends thru the entire adjustable rail clamp assembly  12  and a lower portion  123  of the adjustable post  17  exits out a non-cylindrical bore hole  111  of the lower jaw member  58 . As will be explained in detail later, the clockwise rotation of the jaw drive member  62  drives the upper jaw member  60  downward forcing the upper jaw member  60  and the lower jaw member  58  toward one another to engage the table rail  15 . 
         [0034]    Referring to  FIGS. 2 ,  3 ,  3 A,  3 B, the upper jaw member  60  preferably has an outside surface that is generally D shaped. Other shapes are also contemplated. Further, the upper jaw member  60  may have a generally D shaped hollow area  80  disposed along its longitudinal axis. The upper end of the upper jaw member  60  preferably includes a semicircular bored section  84  having a guide slot  85 . Also, the upper jaw member  60  preferably has a upper lip  81  that protrudes outwardly and downwardly from the upper jaw  60  for engaging the table rail  15 . The upper jaw member  60  is preferably positioned over the lower jaw member  58 . A flat portion  82  of the generally D-shaped hollow area  80  is sized to co-operate with a flat portion  109  of the lower jaw member  58  shown in  FIG. 6D . 
         [0035]    Referring to  FIGS. 2 ,  3  and  4 , the jaw drive member  62  is preferably rotatably mounted to the upper jaw member  60  by an annular flange  90  formed at the lower end of the jaw drive member  62 . The guide slot  85  in the upper end of the upper jaw member  60  is sized to receive the annular flange  90  of the jaw drive member  62 . During assembly, the annular flange  90  of the jaw drive member  62  is laterally moved into the guide slot  85  of the upper end of the upper jaw member  60 . This cooperation prevents vertical separation of the upper jaw carrying member  60  from the jaw drive member  62  while permitting rotation of the jaw drive member  62  relative to the upper jaw member  60 . As the upper jaw member  60  is driven downwardly to engage the top of table rail  15 , the flat portion  82  of the opening  80  in the upper jaw member  60  slides over the flat side  109  of the lower portion  103  of the lower jaw member  58 . This prevents rotational movement of the upper jaw member  60  as the jaw drive member  62  is rotated. 
         [0036]    As shown in  FIG. 4 , the jaw drive member  62  includes a set of internal thread set  91  formed within a cylindrical bore  92 . A diameter  93  of the thread set  91  is larger than a diameter  95  of the upper portion of the cylindrical bore  92  above the thread set  91 . Also, as shown in  FIG. 4A , the top of the jaw drive member  62  is formed with four protruding areas  96 ,  97 ,  98 ,  99 . 
         [0037]    Referring to  FIGS. 5A ,  5 B, and  5 C, a pair of manual control handles  86 ,  87  are disposed at the uppermost end of the jaw drive member  62 . The control handles  86 ,  87  may be generally U-shaped and preferably pivotally fastened to the jaw drive member  62  by pins  88 ,  89 . As shown in  FIG. 5A , the top of the jaw drive member  62  is formed with the four protruding areas  96 ,  97 ,  98 ,  99 . The protruding area  96 ,  99  may serve as bearings for the pins  88 ,  89 . The control handles  86 ,  87  permit operation of the rail clamp via rotation of the control handles  86 ,  87 . 
         [0038]    Referring to  FIGS. 6 ,  6 A,  6 B,  6 C, and  6 D, an upper exterior portion  100  of the lower jaw member  58  is preferably generally circular in shape with a cylindrical bore  101  for receiving a circular portion  120  ( FIG. 7 ) of the adjustable post  17 . An exterior lower portion  102  of the cylindrical portion  100  of the lower jaw member  58  is threaded. Referring to  FIG. 6B  and  FIG. 6D , after the threaded portion  102  of the lower jaw member  58 , an exterior shape  103  of the lower jaw member  58  may transition from the circular shape  100  into a general D shape  109 . The cylindrical bore  101  may continue through D shaped portion  103  for receiving the circular portion  120  of the adjustable post  17 . Referring to  FIGS. 6 and 6B , a lower portion  104  of the lower jaw member  58  is preferably D shaped. The lower portion  104  of the lower jaw member  58  has a rectangular bore  111  for receiving a rectangular portion  123  of the adjustable post  17 . A lower lip  106  protrudes outwardly and upwardly from the lower jaw member  58  for engaging the table rail  15 . 
         [0039]    The exterior upper portion  100  of the lower jaw member  58  has two spaced apart slots  107 ,  112 . In between the spaced apart slots  107 ,  112 , the lower jaw member  58  has a plurality of frustum-conical holes  108  for receiving a curved surface member  142  shown on  FIG. 8 . 
         [0040]    As shown in  FIG. 6 , the lower jaw member  58  has a reciprocal set of threads  102  which surround the lower portion of the lower jaw member  58 . Referring to  FIGS. 2 ,  4 , and  6 , the threads  91  in the jaw drive member  62  and the threads  102  of the lower jaw member  58  preferably engage each other as the jaw drive member  62  is manually rotated in a clockwise direction. Rotation of the jaw drive member  62  drives the upper jaw member  60  downwardly, forcing the lower lip  106  of the lower jaw member  58  and the upper lip  81  of the upper jaw member  60  toward one another to engage the table rail  15 . The jaw drive member  62  is rotated until the lower jaw lip  106  on lower jaw member  58  and the upper jaw lip  81  of the upper jaw member  60  securely tighten against the rail  15 . 
         [0041]    The counter clockwise rotation of the jaw drive member  62  causes the upper jaw member  60  to recede from the lower jaw member  58 . Continued counter clockwise rotation of the jaw drive member  62  may cause complete separation of the thread sets  91 ,  102 . With the upper jaw member  60  disengaged from the lower jaw member  58 , the thread sets  91 ,  102  become exposed for cleaning The reduction in diameter at a location  94  of the jaw drive member  62  shown in  FIG. 4  contacts an angled periphery surface  113  of the lower jaw member  58  to control the extent of opposing movement of the lower jaw member  58  and the upper jaw member  60 . 
         [0042]      FIG. 7  illustrates at least one aspect of the adjustable post  17 . As shown in  FIG. 7 , the upper portion  120  of the adjustable post  17  is preferably generally cylindrical. The upper portion  120  of the adjustable post  17  includes at least a groove  121 . Those skilled in the art will realize that more than one groove  121  is preferable. Further, the upper portion  120  of the adjustable post  17  may include a plurality of pin holes  122  for receiving pins to position universal clamps  21  on the end of the adjustable post  17 . 
         [0043]    The lower portion  123  of the adjustable post  17  is preferably non-cylindrical. Referring to  FIG. 2  and  FIG. 6 , the adjustable post  17  is inserted into the bored out section  101  of the lower jaw member  58  with the non-cylindrical end  123  inserted first until the non-cylindrical end engages the non-cylindrical bored hole  111  in the lower jaw member  58 . The engagement of the non-cylindrical lower section  123  of the adjustable post  17  with the non-cylindrical bore hole  111  of the lower jaw member  58  prevents the adjustable post  17  from rotating. 
         [0044]    Referring again to  FIGS. 2 ,  3  and  4 , the adjustable the adjustable post  17  extends upwardly through a hollow area  80  in the upper jaw member  60  and the cylindrical bore  92  formed in the jaw drive member  62 . 
         [0045]      FIG. 8  is a cross sectional view of one aspect of the slide locking mechanism  140 . The slide locking mechanism  140  preferably includes a slide lock sleeve  141 , a spring  143 , snap rings  144 ,  147  and a plurality of curved surface members  142  such as ball bearings. The slide locking mechanism  140  permits a quick adjustment of the retractor assembly height through the longitudinal adjustment of the adjustable post  17 . Slide lock sleeve  141  is bored to have a minimum opening to allow the slide lock sleeve  141  to be slidably inserted over the upper portion  100  of the lower jaw member  58 . To retain the slide lock sleeve  141  of the slide locking mechanism  140  on the upper portion  100  of the lower jaw member  58 , snap rings  144 ,  147  may be inserted into the slot  107  and the slot  112  of the lower jaw member  58 . The slots  107  and  112  are spatially located on the upper portion  100  of the lower jaw member  58 . The snap ring  147  preferably limits upward longitudinal movement of slide lock sleeve  141 . The snap ring  144  preferably limits the downward longitudinal movement of slide lock sleeve  141 . 
         [0046]    The slide lock sleeve  141  preferably has a bore comprised of several inner diameters. The slide lock sleeve  141  has a first axial bore  148 . After the bore  148 , preferably a second reduced dimension bore  149  may be made in the slide lock  141  forming an internal shoulder  150 . The internal shoulder  150  is of such a dimension that it engages the snap ring  147 , thereby limiting upward longitudinal movement of the slide lock sleeve  141 . Preferably after the second bore  149  forms the shoulder  150 , a third bore channel  146  may be formed in the slide lock sleeve  141  preferably having a greater diameter bore than bore  149 . The channel  146  has an angular transition  152  to a fourth axial bore  145 . The axial bore  145  preferably has a bore diameter greater than groove  146  diameter and the bore diameter of the channel  146  is slightly greater than the outside diameter of the upper portion  100  of the lower jaw member  58  allowing the slide lock sleeve  141  to slidably move over the upper portion  100  of the lower jaw member  58 . After the bore  145 , the slide lock sleeve  141  may have a fifth axial bore  153 . The diameter of the axial bore  153  is preferably greater than the diameter of the bore  145  thus creating a shoulder  154 . Bore  153  is capable of receiving a spring  143 . The spring  143  is bounded by the shoulder  154  on the upper end and the snap ring  144  on the lower end. 
         [0047]    As shown in  FIG. 8 , a plurality of curved surface members  142 , for example ball bearings, are inserted in the frustum-conical holes  108  in the lower jaw member  58 . As shown in  FIG. 6C , the frustum-conical holes  108  preferably are provided with an end diameter  110  that is smaller than the diameter of the curved surface members  142 , but large enough to permit a portion of the curved surface members  142  to extend into the opening  101  of the lower jaw member  58 . 
         [0048]    As shown in  FIGS. 2  and  FIG. 8 , the adjustable post  17  is inserted into the space  101  of the lower jaw member  58 . In the locked position of the slide locking mechanism  140 , the bore  145  of the slide lock sleeve  141  engages the curved surface members  142  which are located in the frustum-conical holes  108  of the lower jaw member  58  causing the curved surface members  142  to partially protrude into the space  101  of the lower jaw member  58  and thus engage the groove  121  of the adjustable post  17 . In the locked position, the spring  143  biases the shoulder  150  of the slide lock sleeve  141  against the snap ring  147 . 
         [0049]    To place the sliding lock mechanism in the unlocked position, the slide lock sleeve  141  is depressed in a downward direction, compressing the spring  143  against the snap ring  144 . The slide lock sleeve  141  moves downward until the channel  146  of the slide lock sleeve  141  aligns with the frustum-conical holes  108  in the lower jaw member  58  permitting the curved surface members  142  to partially exit the frustum-conical holes  108  and thereby permitting the curved surface members  142  to withdraw from the groove  121  in the adjustable post  17 . The withdrawal of the curved surface members  142  from the groove  121  in the adjustable post  17  frees the adjustable post  17  from its locked position and permits the longitudinal adjustment of the adjustable post  17  either up or down. Holding the slide lock sleeve  141  in the depressed position permits the adjustable post  17  to be adjusted without intermediate engagement of the curved surface members  142  into the grooves  121  of the adjustable post  17 . 
         [0050]    When the adjustable post  17  is longitudinally adjusted such that the groove  121  of the adjustable post  17  does not align with the bore  145  of the slide lock sleeve  141  and the adjustable post  17  is in the unlocked position, slide lock sleeve may be released returning it to its unbiased position. In this position, the bore  145  engages the curved surface members  142  and urges curved surface members  142  against the adjustable post  17 . The curved surface members  142  may then engage the outer surface of the adjustable post  17 . With slide lock sleeve  141  in this position, the adjustable post  17  may then be adjusted until the curved surface members  142  engage the next groove  121  in the adjustable post  17  and lock the adjustable post  17  at the desired position. 
         [0051]    An alternative embodiment of the technology for rotating jaw drive member  62  is illustrated in  FIGS. 9 through 11 .  FIG. 9  illustrates the same elements of  FIG. 4  of the jaw drive member  62 , however the four protruding areas  96 ,  97 ,  98 ,  99  shown in  FIG. 4A  on the top of the jaw drive member  62  and the pair of manual control handles  86 ,  87  disposed at the uppermost end of the jaw drive member  62  have been eliminated. Referring to  FIG. 9 , the upper portion of the jaw drive member  62  is formed with a plurality of ratchet teeth  260  on the periphery of the drive member  62 . 
         [0052]      FIG. 10  illustrates a side view of a reversible ratchet assembly  300 . The reversible ratchet assembly  300  can engage the ratchet teeth  260  on the jaw drive member  62 . With the reversible ratchet assembly  300  engaged on the ratchet teeth  260  of the jaw drive member  62 , the reversible ratchet assembly  300  can rotate the jaw drive member  62  in a clockwise or a counter-clockwise direction. The clockwise rotation of the jaw drive member  62  drives the upper jaw member  60  downwardly, forcing the lower lip  106  of the lower jaw member  58  and the upper lip  81  of the upper jaw member  60  toward one another to engage the table rail  15 . The jaw drive member  62  is rotated until the lower jaw lip  106  on the jaw drive member  62  and the upper jaw lip  81  of the upper jaw member  60  securely tighten against the rail  15 . 
         [0053]    With the reversible ratchet assembly  300  engaged on the ratchet teeth  260  on the jaw drive member  62  and set to ratchet in a counter-clockwise direction, the counter-clockwise rotation of the jaw drive member  62  causes the upper jaw member  60  to recede from the lower jaw member  58  untightening the lower jaw lip  106  on the jaw drive member  62  and the upper jaw lip  81  of the upper jaw member  60  from the rail  15 . 
         [0054]    The reversible ratchet assembly  300  includes a handle  220  operatively connected to a head  270 . The head  270  defines a bore  290  for receiving the ratchet teeth  260  on the jaw drive member  62 .  FIG. 11  illustrates the engagement of the reversible ratchet assembly  300  with the ratchet teeth  260  on the jaw drive member  62 . The head  270  includes a pawl  210 , a compression spring  266 , and a ball  264 . The pawl  210  is rotatable about the axis of a pawl pin  230 . The pawl  210 , the compression spring  266 , and the ball  264  are retained in the head  270  by a cover plate  275 . 
         [0055]    The pawl  210  has a first side  276  with a pair of engagement teeth  254 ,  250  and a second opposite side  277  with a pair of cam surfaces  261 ,  267 . In  FIG. 11 , the engagement tooth  254  is engaged with the ratchet teeth  260 . For clockwise rotation of the jaw drive member  62 , the pawl  210  may rotate in its operating condition between an engaged position with the engagement tooth  254  engaged with the ratchet teeth  260  and a disengaged position. For counter-clockwise rotation of the jaw drive member  62 , the pawl  210  may rotate in its operating condition between an engaged position with the teeth  250  engaged with the ratchet teeth  260  and a disengaged position. 
         [0056]    During ratcheting movement of the reversible ratchet assembly  300 , the pawl  210  oscillates between engaged and disengaged positions. Upon rotation from the engaged position of the engagement teeth  254  with the ratchet teeth  260  of the jaw drive member  62 , the pawl  210  second opposite side  277  cam surface  267  interacts with a bias mechanism in which the ball  264  is biased against pawl  210  by the compression spring  266 . As the engaged teeth of the ratchet teeth  260  cams past the engagement tooth  254 , the spring  266  causes the ball  264  to ride on the second cam surface  267  to urge the pawl  210  back toward position for engagement with the next tooth of the ratchet teeth  260 . 
         [0057]    To rotate the jaw drive member in the counter-clockwise direction, the pawl  210  can be rotated so the engagement tooth  250  engages the ratchet teeth  260 . Upon rotation from the engaged position of the engagement teeth  250  with the ratchet teeth  260  of the jaw drive member  62 , the pawl  210  second opposite side  277  cam surface  261  interacts with a bias mechanism in which the ball  264  is biased against the pawl  210  by the compression spring  266 . As the engaged teeth of the ratchet teeth  260  cams past the pawl tooth  250 , the spring  266  causes the ball  264  to ride on the second cam surface  261  to urge the pawl  210  back toward position for engagement with the next tooth of the ratchet teeth  260 . 
         [0058]    The ratcheting of reversible ratchet assembly  300  can ratchet the jaw drive member in a  62  in a clockwise or counter-clockwise rotation depending on the position of pawl  210 . 
         [0059]    Referring to  FIGS. 12-15 , an alternative embodiment of a locking device to allow for height adjustment of adjustable post  17  is illustrated. In  FIG. 12 , an alternate embodiment for the lower jaw member  58  is illustrated. An end portion  125  of the lower jaw member  58  has a plurality of slots  130  in the sidewalls of the lower jaw member  58 . The slots  130  in the lower jaw member  58  form a plurality of flexible fingers  135 . 
         [0060]    Referring to  FIGS. 13-15 , a locking device  170  using a cam tightened clamp can be used to lock the height of the adjustable post  17 . The locking device includes a clamp  175 . The clamp  175  includes a cylindrical passage  176  for receiving the slots  130  in the end portion  125  of the lower jaw member  58 . The cylindrical passage  176  is defined by a broken cylindrical surface  177 . The cylindrical surface  177  is broken along two parallel faces  178  and  179  which run the length of the clamp  175  to define a gap  180 . 
         [0061]    The clamp  175  includes a cam lever  182  as shown in  FIGS. 13 and 14 . The cam lever  182  is pivotally connected to a shaft  155  through a bore  164  by a pin  156 . The shaft  155  operatively connects the cam lever  182  to the clamp  175 . The cam lever  182  is pivotally moveable about the shaft  155  between an open position and a closed position. An outer edge  160  of a cam portion  162  of the cam lever  152  is eccentric such that the distance between the center of the bore  164  in the cam lever  152  and a top  166  of the clamp  175  increases as the cam lever is moved from its open position to its closed position. Movement of the cam lever  182  towards its closed position closes the gap  180  between the parallel faces  178  and  179 . As the parallel faces  178 ,  179  of clamp  175  come closer together, the area circumscribed by the cylindrical passage  176  is constricted and the circumference of the flexible fingers  135  is reduced to grip the adjustable post  17  locking its movement. 
         [0062]    Rotation of the cam lever  182  to its open position increases the cylindrical passage  176  allowing the flexible fingers  135  of the lower jaw member  58  to expand and release the grip on the adjustable post  17 . With the cam lever  182  in the open position, adjustable post  17  is free to move allowing for adjustment. 
         [0063]    While the invention has been described with reference to preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.