Abstract:
The present invention is a mechanism for releasing a positioning device from a locked position. The positioning device has a moveable wedge urged against a rotatable cammed member which permits rotatable travel of the cammed member in only one direction. The releasing mechanism comprises a lever attached to the wedge and engageable with the cammed member. Engaging the lever with the cammed member urges the wedge away from the cammed member to permit rotation of the cammed member in either direction.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
   This application is a continuation-in-part of U.S. application Ser. No. 09/864,681 filed on May 24, 2001, now U.S. Pat. No. 6,572,540. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to a locking mechanism. In particular, the present invention relates to a cam and wedge locking mechanism to selectively position a surgical retractor blade attached to a retractor mounting apparatus. 
   During many types of surgical procedures it is necessary to use a retractor to hold back tissue proximate a surgical incision. The retractor enables a surgeon to work at and in the surgical incision. Retractors typically include a blade and an arm, such as a shaft, to which the blade is attached. The retractor is generally held in place by attachment to a retractor support apparatus that is positioned over a support surface, such as an operating table. The retractor support apparatus is usually attached to a side rail located along one or more sides of the operating table by a clamping device, such as a fulcrum clamp or a cammed clamp. 
   Current retractors are not easy to manipulate and position over the surgical incision because the arm is typically a solid inflexible rod. Clamping mechanisms to lock the retractors in a precise location are typically cumbersome and require complex maneuvering that may increase the risk of injury to the patient. Typically, adjustment of the retractor occurs at the clamping device which attaches the retractor to the sides of the operating table. Positioning the retractor at this location remains challenging since the clamping device may be difficult to operate, or be located at a place that may increase the risk of contamination to the patient. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention is an automatic locking mechanism for selectively positioning a retractor blade of a retractor apparatus. The invention includes a retractor blade attached to a cam and wedge locking mechanism. The cam and wedge locking mechanism permits rotational movement of the retractor blade from a first position to a second position, but prohibits reverse rotation while the wedge engages the cam. A releasing mechanism attaches to the locking mechanism to urge the wedge away from the cam, permitting reverse rotation of the retractor blade. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a first embodiment of the present invention with a retractor blade in a first position (detailed) and a second position (broken lines). 
       FIG. 2  is a cross-sectional view of the first embodiment of the present invention with the retractor blade in a first position (detailed) and a second position (broken lines). 
       FIG. 3  is a perspective view of a second embodiment of the present invention with a retractor blade in a first position (detailed) and a second position (broken lines) along with a lever of a releasing mechanism in a non-engaging position (broken lines) and an engaging position (detailed). 
       FIG. 4  is a cross-sectional view of the second embodiment of the present invention with the retractor blade in a first position (detailed) and a second position (broken lines). 
       FIG. 5  is a exploded perspective view of the second embodiment of the present invention. 
   

   DETAILED DESCRIPTION 
   A retractor apparatus of the present invention is generally indicated at  10  in  FIG. 1 . A locking mechanism of the present invention is generally indicated at  12 . The locking mechanism  12  is designed to automatically permit rotational movement of a retractor blade  50  in one direction only, from a first upright position  16  to a second downward position  18  (shown in broken lines), while the locking mechanism  12  is engaged. The locking mechanism  12  includes a cammed member  14 , a wedge member  20 , and a spring  22 , all enclosed within a housing  24  as illustrated in  FIG. 2 . 
   The cammed member  14  includes a through-bore  26 , the through-bore  26  defining an axis of rotation  27  for the cammed member  14 . The housing  24  includes first and second mating apertures  28 , only one of which is illustrated. The mating apertures  28  are aligned with each other by being positioned on opposing wall sections. The cammed member  14  is positioned within the housing  24  such that the through-bore  26  aligns with each mating aperture  28 . 
   A securing pin  30  is inserted through the mating apertures  28  and the through-bore  26  of the cammed member  14 , thereby rotatably securing the cammed member  14  to the housing  24 . Once secured within the housing  24 , the cammed member  14  is freely rotatable between the first upright position  16  and the second downward position  18 . 
   The first upright position  16  is defined by a first top side  32  of the cammed member  14  contacting the housing  24 , while the second downward position  18  is defined by a second bottom side  34  of the cammed member  14  contacting the housing  24 . It should be noted, however, that the terms ‘top’ and ‘bottom’ are arbitrary terms, and are used for illustrative purposes with reference to the Figures. 
   The cammed member  14  further includes a cammed surface  36  having a decreasing radius from point A to point B as defined from axis  27 . The cammed surface  36  may be the result of an eccentric construction (wherein the axis of rotation is in an offset position) or wherein the cam surface  36  is a lobe offset from the axis of rotation or other construction known in the art. Point A is defined as a point on the cammed surface  36  where an inclined surface  40  of the wedge  20  contacts the cammed member  14 , corresponding to the cammed member  14  in the first upright position  16 . Point B is defined as a point on the cammed surface  36  where the inclined surface  40  of the wedge  20  contacts the cammed member  14 , corresponding to the cammed member  14  being in the second downward position  18 . 
   The wedge  20  is a movable member situated within the housing  24  such that the inclined surface  40  of the wedge  20  is capable of contacting the cammed surface  36  of the cammed member  14 . The wedge  20  is movable through an infinite number of positions while contacting the wedge  20 . A first initial engagement position  42  and a second extended position  44  in broken lines is illustrated in  FIG. 2 . The first initial engagement position  42  is defined as the position wherein the retractor blade  50  is at a first upright position and the wedge  20  contacts the cammed member  14 . The second extended position  44  is defined as the position wherein the retractor blade  50  is at the second downward position  18  and further forward movement of the wedge  20  is prohibited. The wedge is also movable away from the cammed member to a non-engaging position (not shown), wherein the wedge is disengaged from the cammed member  14 , and the retractor blade  50  is freely rotatable in either direction. 
   A height of the inclined surface  40  of the wedge  20  is lowest at a first forward end  46  of the wedge  20 , and increases down the length of the wedge  20 . 
   The compressible spring  22  urges the wedge  20  toward the second extended position  44  and against the cammed member  14 , thereby contacting the inclined surface  40  of the wedge  20  with the cammed surface  36  of the cammed member  14 . A finger tab  48  is attached to the wedge  20 . The finger tab  48  allows a user to withdraw the wedge  20  away from contacting the cammed member  14  and toward the first position  42 . 
   In operation, a force is applied to the finger tab  48  which overcomes the force of the compressible spring  22 , thereby allowing the wedge  20  to withdraw away from the cammed member  14  toward and even beyond the first initial engaging position  42 . Upon moving past the first non-engaging position, the cammed member  14  is freely rotatable in either direction. The retractor blade  50 , and thus the cammed member  14  is manually positionable in the first upright position  16  by engaging the finger tab  48  and urging the wedge  20  toward the initial engaging position  42 . Upon removal of the force applied to the finger tab  48 , the compression spring  22  urges the wedge  20  into contact with the cammed member  14 . Upon the wedge  20  engaging the cammed member  14 , the cammed member  14  is only rotatable from the first upright position  16  to the second downward position  18 , and not in reverse. 
   As the cammed member  14  rotates from the first position  16  to the second position  18 , the decreasing radius from point A to point B of the cammed surface  36  allows the compression spring  22  to urge the wedge  20  toward the second extended position  44 , the wedge  20  in continuous contact with the cammed member  14 . Reverse-rotation of the cammed member  14  in the direction from the second downward position  18  to the first upward position  16  is not possible because the cammed surface  36  of the cammed member  14  will be forced against the inclined surface  40  of the wedge  20 . The relative increase in length of the radius of the cammed member  14 , from point B to point A, which defines the cammed surface  36 , in conjunction with the increase in height of the wedge  20 , prohibits rotatable travel of the cammed member  14  in the reverse direction. 
   To rotate the cammed member  14  toward the first upright position  16 , a force is applied to the finger tab  48  to overcome the force of the compression spring  22  allowing the wedge  20  to slide toward the first initial engaging position  42 . When the wedge  20  moves past the initial engaging position  42 , the wedge  20  disengages from the cammed member  14 , and the cammed member  14  is freely rotatable in either direction. The cammed member  14  can then be positioned in the first upright position  16 . 
   In the preferred embodiment of the present invention, the retractor blade  50  is attached to the cammed member  14 . As illustrated in each figure, the retractor blade  50  has a general “L”-shaped configuration with a first leg  52  attached to the cammed member  14 . A second leg  54  of the retractor blade extends past the locking mechanism  12 , and is configured to retract flesh, such as skin and muscle tissue, in a selected position during a surgical operation. Preferably, the retractor apparatus  10  includes an arm  56  having a proximate end  58  and a distal end  60 . The housing  24  of the retractor apparatus  10  is attached to the proximate end  58  of the arm  56 . 
   In use, the retractor blade  50 , which is in the first upright position  16 , is positioned within the surgical incision, and the distal end  60  of the arm  56  is secured to the operating table (not shown). The surgeon is then able to further position the retractor blade  50  by rotating retractor blade  50 , and thus the cammed member  14 , toward the second downward position  18 . 
   When a selected position of the retractor blade  50  is obtained, there being an infinite number of selectable positions between the first upright position  16  and the second downward position  18 , the retractor blade  50  is held at the selected position due to the automatic locking mechanism  12 . A load on the retractor blade  50 , which is provided by the retained flesh, tends to urge the retractor blade  50  in the reverse direction toward the first upright position  16 . However, when the wedge  20  engages the cammed member  14 , rotation in the reverse direction is not permitted, and the flesh is retained at the selected position. Thus, the retractor blade  50  is automatically held at the selected position. The retractor blade  50  can be further positioned to increase access to the operable area if the surgeon desires by further rotating the retractor blade  50 , and thus the cammed member  14 . Any amount of rotation of the cammed member  14  in the direction of the second downward position  18  will lock the cammed member  14  at that position. 
   To reposition the retractor blade  50  toward the first upright position  16 , a force to overcome the compression spring  22  is applied to the finger tab  48  urging the wedge  20  towards the first initial engaging position  42 . As the wedge  20  travels towards the initial engaging position  42 , the relative height of the inclined surface  40  decreases allowing the cammed member  14 , which has a tendency to rotate toward the first upright position  16  due to the load bearing on the retractor blade  50 , to rotate in the reverse direction because of the relatively increasing radius of the cammed surface  36  contacting the relatively decreasing height of the inclined surface  40  of the wedge  20 . Any movement of the wedge  20  toward the first non-engaging position will cause the cammed member  14  to reverse rotate and thus affecting the position of the retractor blade  50  towards the first upright position  16 . 
   To remove the retractor apparatus  10  upon completion of the surgical procedure, the finger tab  48  is used to position the wedge  20  past the initial engaging position  42 , thus allowing the cammed member  14  to be freely rotatable. The retractor blade  50  is brought to the first upright position  16 , and the apparatus  10  is removed from the surgical site. 
   An alternative embodiment of the present invention is generally indicated at  100  in  FIGS. 3 through 5 . A releasing mechanism for use with the alternative embodiment  100  is generally indicated at  110  while a locking mechanism is generally indicated at  112 . The locking mechanism  112  is designed to automatically permit rotational movement of a retractor blade  114  in one direction only, from a first upright position  116  to a second downward position  118  (shown in broken lines), while the locking mechanism  112  is engaged. The releasing mechanism  110  provides a means to selectively position the retractor blade between the second downward position  118  to the first upright position  116  when a retraction force is exerted on the retractor blade  114 . 
   The locking mechanism  112  includes a cammed member  120 , a wedge  122 , and a spring  124 , all enclosed within a housing  126 . The cammed member  120  includes a through-bore  128  an axis of rotation  130  for the cammed member  120 . The housing  126  includes first and second mating apertures  132 , only one of which is illustrated. The mating apertures  132  are aligned with each other by being positioned on opposing wall sections of the housing  126 . The cammed member  120  is positioned within the housing  126  such that the through-bore  128  aligns with each mating aperture  132 . 
   A securing pin  134  inserts through the mating apertures  132  and the through-bore  128  of the cammed member  120 , thereby rotatably securing the cammed member  120  to the housing  126 . Once secured within the housing  126 , the cammed member  120  is freely rotatable between the first upright position  116  and the second downward position  118 . 
   The cammed member  120  further includes a cammed surface  136  having a decreasing radius from point D to point E as defined from axis  130 . The cammed surface  136  may be the result of an eccentric construction (wherein the axis of rotation is in an offset position) or wherein the cam surface  136  is a lobe offset from the axis of rotation or other construction known in the art. Point D is defined as a point on the cammed surface  136  where an inclined surface  138  of the wedge  122  contacts the cammed member  120 , corresponding to the cammed member  120  in the first upright position  116 . Point E is defined as a point on the cammed surface  136  where the inclined surface  138  of the wedge  122  contacts the cammed member  120 , corresponding to the cammed member  120  being in the second downward position  118 . 
   The wedge  122  is a movable member situated within the housing  126  such that the inclined surface  138  of the wedge  122  is capable of contacting the cammed surface  136  of the cammed member  120 . The wedge  122  is movable through an infinite number of positions while contacting the cammed member  120 . The infinite number of positions is best explained by a first initial engagement position  140  and a second extended position  142 . As illustrated in  FIG. 4 , the first initial engagement position  140  is defined as the position wherein the retractor blade  114  is at the first upright position  116  and the wedge  122  contacts the cammed member  120 . The second extended position  142  is defined as the position wherein the retractor blade  114  is at the second downward position  118  and further forward movement of the wedge  122  is prohibited. The wedge  122  is also movable away from the cammed member  120  to a non-engaging position (not shown), wherein the wedge  122  is disengaged from the cammed member  120 , and the retractor blade  114  is freely rotatable in either direction. A height of the inclined surface  138  of the wedge  122  is lowest at a first forward end  144  of the wedge  122 , and increases down the length of the wedge  122 . 
   The compressible spring  124  urges the wedge  122  toward the second extended position  142  and against the cammed member  120 , thereby contacting the inclined surface  138  of the wedge  122  with the cammed surface  136 . The releasing mechanism  110  pivotally attaches to the wedge  122 . The releasing mechanism  110  allows a user to incrementally urge the wedge  122  toward the first position  140 , away from contacting the cammed member  120 , thus incrementally allowing the retractor blade  114  to travel from the second position  118  toward the first position  116 . 
   The releasing mechanism  110  includes a lever  146  having an aperture  148  through which a pin  150  extends to pivotally secure the lever  146  to the wedge  122 . The pin  150  slidably disposes within a slotted aperture  152  positioned within the housing  126 . The slotted aperture  152  includes flattened surfaces  154  on either side upon which the lever  146  slidably engages. As illustrated in  FIG. 3 , the lever  146  is pivotable between a non-engaging position (dashed) and an engaging position (solid). Positioning the lever  146  from the non-engaging position toward the engaging position, the lever  146  engages an abutting surface  156  of the cammed member  120 . A torsional spring  158  is provided to retain the lever  146  in the non-engaging position during use to prevent the lever  146  from unwanted engagement with the abutting surface  156 . 
   In operation, the releasing mechanism  110  disengages the wedge  122  from the cammed member  120 . The lever  146  is positioned to fully engage the abutting surface  156 , which overcomes the force of the compressible spring  124 , thereby allowing the wedge  122  to withdraw away from the cammed member  120  toward and even beyond the first initial engaging position  140 . Upon moving past the first non-engaging position, the cammed member  120  is rotatable in either direction against the frictional force of the lever  146  engaging the abutting surface  156 . The retractor blade  114 , and thus the cammed member  120 , is manually positionable to the first upright position  116 . Upon releasing the lever  146 , the torsional spring  158  urges the lever  146  into the non-engaging position, and the compression spring  124  urges the wedge  122  into contact with the cammed member  120 . Upon the wedge  122  engaging the cammed member  120 , the cammed member  120  is only rotatable from the first upright position  116  to the second downward position  118 , and not in reverse. 
   As the cammed member  120  rotates from the first position  116  to the second position  118 , the decreasing radius from point D to point E of the cammed surface  136  allows the compression spring  124  to urge the wedge  122  toward the second extended position  142 , the wedge  122  being in continuous contact with the cammed surface  136 . Reverse-rotation of the cammed member  120  in the direction from the second downward position  118  to the first upward position  116  is not possible because the cammed surface  136  of the cammed member  120  will be forced against the inclined surface  138  of the wedge  122 . The relative increase in length of the radius of the cammed member  120 , from point E to point D, which defines the cammed surface  136 , in conjunction with the increase in height of the wedge  122 , prohibits rotatable travel of the cammed member  120  in the reverse direction. 
   To position the retractor blade  114  toward the first upright position  116 , the releasing mechanism  110  is enacted to urge the wedge  122  to slide toward the first initial engaging position  140 . The lever  146  is positioned to engage the abutting surface  156  of the cammed member  120 . Upon overcoming the force of the compression spring  124 , the wedge  122  will travel away from the cammed member  120 , allowing the cammed member  120  to slightly rotate and reposition the retractor blade  114  in an infinite number of positions. As the wedge  122  travels toward the initial engaging position  140 , the lever  146  slides upon the flattened surfaces  154  of the housing such that the contact with the lever  146  and the abutting surface  156  coincide with the contact of the traveling inclined surface  138  and cammed surface  136 . When the wedge  122  reaches the initial engaging position  140 , the lever  146  must manually disengage the wedge  122  from the cammed member  120  in order for the cammed member  120  to be rotatable in either direction to position the retractor blade  114 . 
   The retractor blade  114 , and use of the retractor apparatus  100  in a surgical setting, is the same as described in relation to the embodiment of retractor apparatus  10 . 
   Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.